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A COMPLETE TREATISE 



ELECTRO-DEPOSITION OF METALS. 



COMPRISING 

ELECTRO-PLATING AND GALVANOPLASTIC OPERATIONS, THE DEPOSITION 

OF METALS BY THE CONTACT AND IMMERSION PROCESSES, 

THE COLORING OF METALS, THE METHODS OF 

GRINDING AND POLISHING, 

AS WELL AS 

DESCRIPTIONS OF THE ELECTRIC ELEMENTS, DYNAMO-ELECTRIC MACHINES, 

THERMO-PILES, AND OF THE MATERIALS AND PROCESSES 

USED IN EVERY DEPARTMENT OF THE ART. 

TRANSLATED FROM YW& GERMAN OF 

Dr. GEOKGE LA^GBELN, 

/i 

PROPRIETOR OP A MANUFACTORY FOR CHEMICAL PRODUCTS, MACHINES, APPARATUS, 

AND UTENSILS FOR ELECTROPLATERS AND OF AN ELECTRO-PLATING 

ESTABLISHMENT, IN LEIPZIG. 

WITH ADDITIONS BY 

Us 
WILLIAM T. BRANNT, 

EDITOR OF "THE TECHNO-CHEMICAL RECEIPT BOOK." 




SECOND EDITION, REVISED AND ENLARGED 

ILL VSTRATED B Y ONE HUNDRED AND THIRTY- EIGHT ENGRA VINGS. 



PHILADELPHIA: 
HENRY CAREY BAIRD & CO., 

INDUSTRIAL PUBLISHERS, BOOKSELLERS, AND IMPORTERS, 
810 WALNUT STREET. 
1894. . 



s-z-^&dy 



I 



V A" 



Copyright by 

HENRY CAREY BAIRD & CO. 

1893. 



~1I I! 















Printed at the COLLINS PRINTING HOUSE, 

705 Jayne Street, 

Philadelphia, U. S. A. 



PREFACE TO THE SECOND AMERICAN EDITION. 



The rapid sale of the first American edition of Dr. George Lang- 
bein's work, "Handbuch der Galvanischen Metall-Niederschlaege" 
and the constant demand for it, are the best proofs of the value and 
usefulness of the book. 

In the second edition, which is now presented to the public, a 
few changes have been made in the arrangement of the text, and 
it has been endeavored to include all practical methods of plating 
metals which have become known since the publication of the 
first edition, as well as the most recent machinery and apparatus, 
so as to make the work still more acceptable and useful to the 
reader. 

The editor is under obligations for information and electrotypes 
to the Hanson & Yan Winkle Co., of Newark, N. J., and the 
Zucker & Levett Chemical Co., of New York, two well-known 
firms dealing in electro-platers' supplies. 

The publishers have spared no expense in the proper illustration 
and the mechanical production of the work, and, like the first 
edition, it has been provided with a copious table of contents and 
a very full index, so as to render reference to any subject prompt 
and easy. 

W. T. B. 

Philadelphia, November 14, 1893. 



PREFACE TO THE FIRST AMERICAN EDITION. 



The art of the electro-deposition of metals has during recent 
years attained such a high degree of development, that it was felt 
that a comprehensive and complete treatise was needed to represent 
the present advanced state of this important industry. In further- 
ance of this object, a translation of Dr. George Langbein's work, 
Volhtaendiges Handbuch der Galvanischen Metall-Niederschlaege, 
is presented to the English reading public with the full confidence 
that it will not only fill a useful place in technical literature, but 
will also prove a ready book of reference and a practical guide for 
the workshop. In fact, it is especially intended for the practical 
workman, wherein he can find advice and information regarding 
the treatment of the objects while in the bath, as well as before 
and after electro-plating. The author, Dr. George Langbein, is 
himself a master of the art, being the proprietor of an extensive 
electro-plating establishment combined with a manufactory of chem- 
ical products, machinery and apparatus used in the industry. 

The results yielded by the modern dynamo-electric machines, to 
which the great advance in the electro-plating art is largely due, are 
in every respect satisfactoiy, and the more so since the need of 
accurate, and at the same time handy, measuring instruments has 
also been supplied. With the assistance of such measuring instru- 
ments, the establishment of fixed rules regarding the current-condi- 
tions for a galvanic bath has become possible, so that good results 
are guaranteed from the start. While formerly the electro-plater 
had to determine the proper current-strength for the depositions in 



VI . PREFACE TO THE FIRST AMERICAN EDITION. 

an empirical manner, by time-consuming experiments, to-day, by 
duly observing the determined conditions and provided with well- 
working measuring instruments, he can at once produce beautiful 
and suitable deposits of the various metals. 

The data referring to these current-conditions, according to mea- 
surements by Dr. Langbein, are given as completely as possible, 
while for the various baths, only formula? yielding entirely reliable 
results have been selected. To most of the baths a brief review of 
their mode of action and of their advantages for certain uses is 
added, thus enabling the operator to select the bath most suita- 
ble for his special purpose. To the few formulae which have not 
been tested, a note to that effect is in each case appended, and they 
are only given with due reserve. 

To render the work as useful as possible, the most suitable for- 
mula? for plating by contact and immersion, as well as the best 
methods for coloring the metals, and the characteristic properties of 
the chemicals used in the industry, are given. However, the pre- 
paration of the chemicals has been omitted, since they can be pro- 
cured at much less expense from chemical works than it would be 
possible for the electro-plater to make them in small quantities, 
even if he possessed the necessary apparatus and the required 
knowledge of chemistry and skill in experimenting. 

It is hoped that the additions made here and there by the trans- 
lator, as well as the chapter on " Apparatus and Instruments," and 
that of " Useful Tables," added by him, may contribute to the use- 
fulness of the treatise. 

Finally, it remains only to be stated that the publishers have 
spared no expense in the proper illustration and the mechanical 
production of the book; and, as is their universal practice, have 
caused it to be provided with a copious table of contents, and a 
very full index, which will add additional value by rendering any 
subject in it easy and prompt of reference. 

W. T. B. 

Philadelphia, July 1, 1891. 



CONTENTS. 



HISTORICAL PART. 
CHAPTER I. 

HISTORICAL REVIEW OF ELECTRO-METALLURGY. 

PAGE 

The method of coating metals by simple immersion known to Zozimus 
and Paracelsus; Luigi Galvani's discovery of the electric contact- 
current, in 1789; Alexander Volta's discovery, in 1799, of the true 
causes of the electric contact-current ...... 1 

Erroneous inference drawn by Galvani from his experiments ; General 
ignorance in regard to the nature of the electric current ; Construc- 
tion of the pile of Volta or the voltaic pile ; Cruikshank's trough 
battery ; Decomposition of water by electrolysis by Nicholson and 
Carlisle, 1800; Wollaston's observation, 1801 2 

Cruikshank's investigations, 1803 ; Brugnatelli's experiments in electro- 
gilding, 1805; Sir Humphrey Davy's discovery of the metals potas- 
sium and sodium, 1807 ; Prof. Oersted's discovery of the deflection of 
the magnetic needle, 1820; Ohm's discovery, in 1827, of the law 
named after him ............ 3 

Faraday's discovery, in 1831, of electric induction; First electro- 
magnetic induction machine constructed by Pixii ; Faraday's electro- 
lytic law laid down and proved in 1833; Production of iridescent 
colors, in 1826, by Nobili ; Production of amalgams of potassium and 
sodium, in 1835, by Bird ; Discovery of the galvanoplastic process, 
in 1838, by Prof. Jacobi ; Claims of priority of invention by Mr. T. 
Spencer and Mr. C. J. Jordan ....... 4 

Labors of the Elkingtons and de Ruolz ; Murray's discovery, in 1840, 
of black-leading ; Introduction of gutta-percha by Dr. Montgomery, 
in 1843 ; First employment, in 1840, of alkaline cyanides by Wright; 
Patent for the deposition of nickel, 1840 ; Origin of the term " electro- 
metallurgy" by Mr. Alfred Smee, 1841 ; Prof. Boettger's discovery, in 
1842, of deposition of nickel from its double salt .... 5 



VI 11 CONTENTS. 

PAGE 

First deposition in 1842, of metallic alloys by de Ruolz ; First use of 
thermo-electricity, in 1843, by Moses Poole; Advances in the Art of 
electro-deposition ; The first magnetic machine that ever deposited 
silver on a practical scale constructed, in 1844, by Woolrych ; Attempts 
since 1854 by Christofie & Co., to replace their batteries by magneto- 
electrical machines; The Alliance machine; Objections to Wilde's 
machine ............ 6 

Dr. Antonie Pacinotti's invention, in I860, of the ring named after him ; 
Siemens's dynamo-machine, 1866 ; Wheatstone's dynamo-machine, 
1867 7 

Introduction, in 1871, of Zenobe Gramme's machine; The Hefner- 
Alteneck's machine, 1872; Siemens & Halske's machine, 1884; S. 
Schuckert's machine, 1884; Various dynamo-electrical machines; 
Investigators and practitioners who have contributed to the improve- 
ment of the electro-chemical process and the perfection of galvano- 
plasty . . . . . . . . . . .8 



II. 

THEOEETICAL PART. 
CHAPTER II. 

MAGNETISM AND ELECTRICITY. 

1. Magnetism. 

Loadstone or magnetic iron ore ; Natural and artificial magnets ; Defi- 
nitions of the magnetic poles and of the neutral line or neutral zone, 
and their positions .......... 9 

Magnetic meridian ; North and south poles; Phenomena of attraction 
and repulsion ; Ampere's theory ; The solenoid . . . .10 

Rejection of Ampere's theory by many scientific men ; Definition of the 
magnetic field . . . . . . . . . .11 

2. Electricity. 

Definition of idio-electrics and of non-electrics ; Gray's discovery, 1727; 
Good and bad conductors ; The electroscope . . . . .11 

Existence of two kinds of electricity ; Vitreous or positive and resinous 
or negative electricity ; Double-fluid hypothesis of electricity . . 12 

Single-fluid hypothesis of electricity ; Coulomb's law ; Series of electro- 
motive force or tension . . . ... . . .13 



CONTENTS. IX 

PAGE 

Production of electricity by the contact of metals and fluids ; Galvanic 
or hydro-electric current ; Galvanic element or galvanic chain ; Elec- 
trical potential ; Electro-motive force . . . . . .14 

Resistance ; Conductivity of metals according to Lazere Weiler ; Quan- 
tity of current — Ohm's law ........ 15 

Essential or internal resistance ; Non-essential or external resistance . 16 

Union or coupling of the elements for electro-motive force or tension, 
and for quantity of current ; Mixed coupling . . . . .18 

Proposition deduced from Ohm's law ; Effects of the electric cmrent . 19 

Electro-Magnetism. 

Pule for determining the direction which the magnetic needle will as- 
sume when placed in any particular position to the conducting wire . 19 

Galvanoscopes, galvanometers, and multipliers ; Astatic galvanometer ; 
Tangent galvanometer ; Sine galvanometer ; Electro-magnets . . 20 

The solenoid; Law of the action of two electrified wires on each other 21 

Induction. 

What is understood by induction . . . . . . .21 

Primary or inductive current ; Secondary or induced current ; Alter- 
nating currents ; Extra currents ....... 22 

Chemical Actions op the Electrical Current — Electrolysis. 

Reduction of the constituents of a fluid by the electric current ; Pure 
water a bad conductor ; Faraday's discovery of the chemical actions 
of the electric current ; Electrolysis ; Electrolyte ; Electrodes . 23 

Anode; Cathode; Ions; Anions; Cations; Atoms; Clausius's theory 
of the molecules . , . . . . . . . .24 

Counter or polarizing current; Faraday's electrolytic laws; Experi- 
ments with the voltameter ........ 25 

Definition of local action ; Electro-chemical equivalents ... 26 

Joule's law; Consumption of power in electrolysis; Electric units 
adopted by the International Congress of 1881 ; Fundamental or C. 
G. S. (centimetre-gramme-second) system; Force or power — dyne 27 

Work — erg. ; Quantity; Potential or electro-motive force; Resistance; 
The ohm ; The ampere ; The volt ; The farad ; The coulomb ; The 
watt ; Definition of the English and of the French horse-power . 28 



CONTENTS. 
III. 

SOURCES OF CURRENT. 
CHAPTER III. 



GALVANIC ELEMENTS — THERMO-PILES — MAGNETO- AND 
DYNAMO-ELECTRIC MACHINES. 

A. Galvanic Elements. 

Voltaic pile ; Trough battery ........ 

Reduction of local action by amalgamating the zinc ; Various methods 

of amalgamating ; Bouant's recommendation . 
Definition and cause of polarization; Smee's element 
Constant elements ; Daniell's element 
Meidinger element ; Grove element .... 

Bunsen elements ....... 

Improved Bunsen cell ...... 

Composition of electropoion ...... 

Location of elements; A. Dupre's substitute for sulphuric 

acids for filling elements ..... 

Manipulation of Bunsen elements ; Advisability of having 

set of porous clay cells ...... 

Renewal of the acids ; Leclancl.e element ; Lallande and Chaperon 

element . . 

Various elements ; Dun's potash element . 
A new element patented in Germany 
Plunge or bichromate batteries ; Bunsen plunge battery 
Fein's bichromate battery ; Keiser & Schmidt's bichromate 
Bichromate element for gilding or silvering small articles 
Stoehrer's battery ....... 



and nitric 



a duplicate 



battery 



PAGE 

'-'9 

30 
31 
32 
33 
34 
35 
36 

37 

38 



40 
41 
42 
43 
44 
45 



B. Thermo-Electric Piles. 

Professor Seebeck's discovery, in 1822, of a new source of electricity ; 
Definition of a thermo-electric couple ; Definition of thermo-elec- 
tricity ; Noe's thermo-electric pile ....... 46 

Clamond's thermo-electric pile . . . . . . . .47 

Hauck's thermo-electric pile . . . . . . . .48 

Gulcher's thermo-electric pile . . . . . . . .49 

Superiority of dynamo-electric machines over thermo-electric piles . 50 



CONTENTS. XI 



C. Magneto- and Dynamo-Electric Machines. 

page 

Faraday's discovery in 1831 ; Magnetic field or the region of the lines 
of force . . . . . . . . . . .51 

What a magneto-electric or dynamo-electric machine actually is ; Pro- 
fessor S. P. Thompson's definition of a dynamo-electric machine ; 
Constituent parts of a dynamo-generator, or a dynamo-electric ma- 
chine proper ........... 52 

Pixii's electrical machine, 1832; Saxton and Clarke's improvements ; 
Dr. W. Siemens's improvement, 1857; Pacinotti's ring conductor; 
Dr. W. Siemens's and Sir C. Wheatstone's discovery ... 53 
Classes of electric generators ; Continuous current machine and alter- 
nating current machine ; Gramme machine and armature . . 54 
Modern Gramme dynamo for galvanoplastic purposes .... 56 

Disadvantage of the Gramme machine ; S. Schuckert's flat-ring ma- 
chine ............ 57 

Fein's dynamo-machine; Brush dynamo and armature . . .58 
Siemens & Halske dynamo-electric machines ..... 60 

Kroettlinger's dynamo-machine . . . . . . . .61 

Lahmeyer dynamo . . . . . . . . v . .62 

Weston dynamo-machine ......... 64 

Hanson & Van Winkle Co.'s new dynamo electro-plating machine . 65 
Hanson & Van Winkle Co.'s bicycle-power plating dynamo; Zucker & 

Levett Chemical Co.'s improved " American Giant" dynamo . . 68 
Various dynamo-machines ; Value of the dynamo and its effect upon 
the electro-plating industry ........ 70 



IV. 

PRACTICAL PART. 
CHAPTER IV. 

ARRANGEMENT OF ELECTRO-PLATING ESTABLISHMENTS IN GENERAL. 

Necessity of sufficient light and thorough ventilation .... 72 

Location of Bunsen elements ; Provision for heating .... 73 
Importance of a good supply of water; Best materials for floors ; Size 

of the operating-room ......... 74 

Grinding- and polishing-rooms ; Prevention of dust in the polishing- 

room ; Location of the transmission carrying the belt pulleys . 75 



Xll CONTENTS. 

Electro-plating Arrangements in Particular. 

page 
What the actual electro-plating plant consists of; Arrangement with 
elements ; Choice of coupling the elements ..... 76 

Proportion of the effective zinc surface of the elements to that of the 
anodes and articles . . . . . . . . .77 

Coupling of elements for solid and thin deposits ; Auxiliary apparatuses 78 
Rheostat, current-regulator, resistance-board or switch-board ; Condi- 
tions upon which the action of the resistance-board is based . . 79 
Horizontal and vertical galvanometers ...... 80 

Location of the resistance-board and galvanometer ; Rheostats patented 

by the Hanson & Van Winkle Company, of Newark, N. J. . . 81 
Indications by the galvanometer ....... 85 

Counter-current ; Rules to be observed in conducting the current; Posi- 
tive or anode-wire ; Negative or object-wire ..... 87 

Vats or tanks ; Wooden vats ........ 88 

Enamelled iron tank ; Agate vessel for gold and other solutions ■ . 89 

Conducting rods .......... 90 

Binding-posts and screws ; Anodes and their arrangement . . .91 
Slinging wires ; Protection of the rods ; Cleansing and rinsing ap- 
paratuses ........... 92 

Dipping or pickling ; Sawdust ; Arrangements with dynamo-electric 

machines ; Rules for setting up and running dynamo-electric machines 93 
Insulation of the object- and anode-wires ......' 94 

Wire-carriers ; Resistance-boards or current-regulators ; Resistance- 
board of the dynamo ; Amperemeter or ammeter ; Voltmeter . . 95 
Coupling of the main object- wire and the main anode- wire with the re- 
sistance-boards, the voltmeter, the shunt, and the baths ... 98 
Feeding the baths . . . . , . . , . .100 

Ground plan of an electro-plating establishment 101 

Lye-kettle; Table for freeing the articles from grease . . .102 

Mode of calculating the thickness of conducting wires for dynamos . 103 

CHAPTER V. 

treatment of metallic articles. 
A. Mechanical Treatment. 

Treatment before electro-plating ; Scratch-brushing ; Various forms of 
scratch- brushes . . . . . . . . . .104 

Treatment of scratch-brushes ; Circular scratch-brushes and their con- 
struction . . . ... . . . . . .106 

Brushes . . . . . . . . . . . .107 

Cleansing by the sand-blast . . • . . . . . 108 



CONTENTS. xiii 

PAGE 

Tumbling box or drum ......... 109 

Polishing articles in the tumbling-drum . . . . . .110 

Grinding ; Grinding disks and their construction . . . .112 

Treatment of the grinding disks ; Vienna lime ; Grinding lathes . . 113 
Execution of grinding . . . . . • . . .114 

Fibres and fibre- brushes; Grinding iron and steel articles . . .115 
Grinding brass and copper castings, sheets of brass, German silver, and 
copper zinc castings, and sheet zinc ; Polishing ; Foot lathes for pol- 
ishing 116 

American double polishing lathe; Lathe manufactured by the Hanson 
& Van Winkle Co., of Newark, N. J. . . '. . . .117 

Belt strapping attachment . . . . . . . . .110 

Polishing materials ; Rouge composition ...... 120 

Burnishing ; Mechanical treatment during and after the electro-plating 

process; Scratch-brushing the deposits ; Effect of scratch-brushing . 121 
Scratch-brushes used for different metals ; Decoctions used in scratch- 
brushing; Scratch-brushing by hand ; Lathe brush . . . . 122 

Cleansing and drying the finished electro- plated objects . . .123 
Sawdust for drying the objects ; Drying plated objects of iron and steel ; 
Removal of moisture from the pores of nickelled iron objects ; Polish- 
ing deposits of nickel, copper and brass, tin, gold and silver, and 
platinum; Operation of burnishing . . . . ■ . . .124 

Various forms of burnishers . . . . . . . .125 

B. Chemical Treatment. 

Pickling ; Mixture for pickling east-iron and wrought-iron objects ; Ex- 
cellent pickle for iron ; To cleanse badly rusted iron objects ; Dura- 
tion of pickling . . . . . . . . . .126 

Pickling zinc objects; Cleansing and brightening copper, brass, bronze, 
tombac, and German silver ; Preliminary pickle ; Bright dipping 
bath; Use of potassium cyanide for pickling ..... 127 

Manipulation of pickled objects ; Dead dip . . . . .128 

Main points in pickling ; Absorbing plant for escaping acid vapors . 129 
Regaining of acid and metal from exhausted dipping baths . . . 130 
Mixture for the production of a grained surface by pickling ; Removal 
of grease ........... 131 

Preparation of lime mixture ; Cleansing with benzine ; Tying the 
objects to metallic wires . . . . . . . . .132 

Removal of oxide from the metallic objects . . . . .133 

Carboy stand 134 



XIV CONTENTS. 

CHAPTER VI. 

PROCESSES OF ELECTRO-DEPOSITION. 

PAGE 

Importance of the constitution of the water used as a solvent ; Spring 
and well water . . . . . . . . . .134 

River water ; Distilled water ; Rain water ; Importance of the purity 
of the chemicals used ......... 135 

Concentration of the baths ; Effects of baths too poor in metal and too 
concentrated . . . . . . . . . . .136 

Stirring up the baths . . . . . . . . .137 

Constant agitation of the baths by mechanical means ; Temperature of 
the baths ; Boiling of baths ; Kettles and boiling pans . . ./ 138 

Working the bath with the electric current in place of boiling; Disso- 
lution of nickel salts dissolving with difficulty ; Filtration of the boiled 
solutions ........... 139 

To secure lasting qualities to the baths ; Choice of anodes ; Alloying of 
the deposit with the basis-metal ; Gore's experiments . . . 140 

Conditions for the good performance of an electrolytic bath ; Reduction 
of metals without a battery (electro-deposition by contact) . . 141 

Dipping baskets . . . . . . . . . .143 

CHAPTER VII. 

DEPOSITION OF NICKEL AND COBALT. 

1. NlCKELLING. 

Growth and popularity of nickel-plating . . . . . . 143 

Properties of nickel ; Nickel baths ; General rules for preparing nickel 

baths 144 

Prepared nickelling salts ; Conducting salts ; Additions to the nickelling 

bath recommended by various experts ; Effect of the presence of 

small quantities of a free acid ....... 145 

JBoric acid as an addition to nickelling and all other baths, and its effects ; 

Determination of the acidity, alkalinity, and neutrality of nickel baths 146 
Formula?, preparation, characteristics, and treatment of nickel baths . 14 7 
Burning or over-nickelling . . . . . . . .148 

Nickel baths containing boric acid; Weston's formula . . .149 

Kaselowsky's formula . . . . . . . . .150 

Nickel baths for certain purposes; Nickel bath for rapid nickelling of 

polished slightly coppered zinc articles ; Nickel bath for iron, brass, 

and copper and sheet zinc and zinc castings . . . . .151 
Recent formulas for nickel baths ; An English formula ; Addition of 

bisulphide of carbon to nickel baths ; Bath for nickelling small articles 152 
Nickel baths without nickel salt ; Nickel anodes ; Objections to the use 

of insoluble anodes . . . . . . . . .153 



CONTENTS. XV 

PAGE 

Use of rolled and cast anodes together in one bath . . . .155 

Cause of the reddish tinge of the anodes ; Suspension of the anodes ; 

Process of electro-nickelling . . . . . . . .156 

Coppering or brassing articles previous to nickelling ; Suspension of the 

objects in the bath ; Suitable current-strength for nickelling . . 157 
Burning or over-nickelling ; Criteria for judging whether nickelling 
progresses with a correct current-strength . . . . .158 

Most suitable current-density for nickelling ; Solid nickelling ; Test for 

sufficiently heavy nickelling ; Arrangement of the anodes . . 159 
Nickelling of flat objects, round or half-round surfaces, smooth articles, 
objects with depressions and hollows, and lamp-feet of cast zinc ; 
General rules for nickelling and other electro-plating processes ; 
Mode of suspending the objects in the bath . . . . .160 

Polarizing phenomena ; Counter or polarizing current . . .161 

Nickelling en masse of small and cheap objects . . . . .162 

Warren's solutions of nickel and of cobalt; Stripping nickelled articles 163 
Remedy against the yellowish tone of the nickelling; Principal phe- 
nomena which may occur in nickelling and the means of avoiding 
them . . . . . . . . . . .165 

Refreshing nickel baths . . . . . . . . .167 

Polishing nickel deposits ; Treatment of nickelled objects which are to 
be left dead ; Nickelling sheet zinc ; Mystery surrounding the nickel- 
ling of sheet-zinc . . . . . . . . ' . .168 

Required conditions for, and the execution of, nickelling sheet-zinc ; 

Grinding and polishing the sheets ; Construction of cloth bobs . 169 

Manner of polishing or grinding the sheets ; Self-acting sheet-polishing 

machines; F. Rauber's sheet grinding and polishing machine . .170 
Freeing the sheets from grease ; Nickelling the sheets . . .173 

Advantage of previous coppering or brassing; Great care required in 
the treatment of the brass bath . . . . . . .174 

Coppering the sheets; Dimensions of the vats for nickelling the sheets 175 
Proportion of anode surface to that of the zinc surface ; Cause of black 

streaks and stains; Augmentation of the metallic content of the bath 176 
Polishing the nickelled sheets ; Nickelling of tin plate, copper and brass 
sheets, and of sheet-iron and sheet -steel . . . . . .177 

Nickelling of wire . . . . . . . . . .178 

Apparatus for nickelling wire . . . . . . . .179 

Nickelling wire gauze ......... 180 

Nickelling of knife-blades, sharp surgical instruments, etc. . . .181 

Nickelling of electrotypes, cliches, etc. ; Baths for hard nickelling . 182 
Process of hard nickelling . . . . . . . . .183 

Treatment of the nickelled plates ; Recovery of nickel from old baths ; 
Urquhart's plan for recovering nickel from old solutions ; To improve 
defective nickelling ; Arrangement of the " doctor" . . .184 



XVI CONTENTS. 

PAGE 

Niekelling by contact and boiling ; Franz Stolba's process of nickeiling 
by contact ........... 185 

Deposition of an alloy containing nickel according to R. Kaiser . .186 

Deposits of nickel alloys, and baths suitable for the purpose ; Nickel 
bronze; French process for the deposition of German silver . .187 

Watt's method for the deposition of German silver .... 188 

2. COBALTING. 

Properties of cobalt . . . . . . . . . .188 

Baths for cobalting ; Cobalting of copper plates for printing ; Determi- 
nation of the quantity of copper dissolved in stripping the cobalt de- 
posit from cobalted copper plates ....... 189 

Warren's cobalt solution ; Cobalt solution recommended by Mr. G. W. 
Beardslee, of Brooklyn, N. Y. ; R. Daub's bath for cobalting small 
fancy articles of copper, brass, or steel . . . . . .190 

Cobalting by contact . . . . . . . . . . . 191 

CHAPTER VIII. 

deposition of copper, brass, and bronze. 
1. Coppering. 



192 
193 



194 
195 



196 
197 



Properties of copper; Copper baths, their composition, preparation 
properties, and treatment ....... 

Hassauer's copper bath ; Copper bath for iron and steel articles . 

Formation of slime on the anodes in a copper bath ; Phenomena ap 
pearing in copper baths containing cyanide . . . 

Baths for coppering zinc articles recommended by Roseleur 

Copper baths -without potassium cyanide ; Weil's copper bath and 
method of coppering . . . . . 

Copper bath recommended by Walenn ; Copper bath according to Pfan 
hauser ; Gauduin's copper bath ...... 

Execution of coppering ; Anodes used ; Scratch-brushing and treatment 
of defective places ; Solid and heavy coppering . . . .198 

Prevention of small, dark, round stains ; O. Schultz's patent to pre- 
vent the formation of stains ; Polishing the deposit of copper . . 199 

Treatment of coppered objects to be coated with another metal ; Cop- 
pering small articles en masse . . . ... . . 200 

Coppering by contact and dipping ; To coat zinc plates with a very thin 
but hard layer of copper ; Bacco's copper bath; Brush-coppering . 201 

Application of a thin film of copper to iron and steel objects ; Copper- 
ing steel pens, needles, eyes, etc. ; Inlaying of depressions of coppered 
art castings with black ...... . 202 



CONTENTS. X\ T ii 

2. Brassing (Cuivre-poli Deposit). 

PAGE 

Constitution and varieties of brass ; Brass baths, their composition, pre- 
paration, properties, and treatment ....... 203 

Rules for baths containing more than one metal in solution ; Brass bath 
according to Roseleur ; Irregular working of fresh brass baths . . 204 

Effect of the addition of arsenious acid to brass baths ; Bath for brass- 
ing iron ............ 205 

On what the color of the brass deposit depends ; Anodes for brass 
baths ............ 206 

Formation of slime on the anodes ; Remedy against defective deposi- 
tion 207 

Bath for brassing zinc exclusively ; Bath for brassing cast iron, wrought 
iron, and steel ; N orris and Johnson's brass bath ; Solution for trans- 
ferring any copper-zinc alloy serving as anode .... 208 

Pfanhauser's bath for brassing all kinds of metals ; Execution of brass- 
ing 209 

Distance of the objects, to be brassed, from the anodes ; Brassing of 
unground iron castings ; Brassing by contact and dipping . . 210 

Inlaying, with black, of brassed articles . . . . , .211 

3. Bronzing. 

Gountier's solution for coating wrought and cast iron with bronze; 

Other bronze baths, and their composition, preparation, and treatment 21 1 
Hess's bath for deposits of tombac ; Execution of brassing . . . 212 

CHAPTER IX. 

DEPOSITION OF SILVER. 

Properties of silver . . . . . . . . . .212 

Silver baths, their composition, preparation, and treatment ; Silver bath 
for a heavy electro-deposit of silver (silvering by weight) ; Prepara- 
tion of the bath with silver chloride . .• . . . .213 

Preparation of the bath with silver cyanide ; Silver bath for ordinary 
electro-silvering . . . . . . . . . 214 

Vats for silver baths ; Treatment of silver baths ; Silver anodes ; Most 
suitable current-strength for silver baths . . . . . .215 

Coupling of the elements ; Indication of the presence of too much or 
not enough potassium cyanide ; Objections to insoluble anodes ; The 
behavior and appearance of the anodes as criteria of the content 
of potassium cyanide in the bath. ....... 216 

Keeping the bath constant by silver anodes ; Proper treatment of baths 
made with chloride of silver . . . . . . . .217 

Gradual thickening of the bath ; Augmentation of the content of silver 

in baths • . .- . . 218 

B 



CONTENTS. 



Determination of the actual content of silver in the bath ; Contrivances 

to keep the objects to be silvered in gentle motion while in the bath 219 
Singular phenomenon in silvering ....... 220 

Remedy against a yellow tone of the silvering ; Execution of silvering ; 
Silvering by weight ; Mechanical and chemical preparation of the 

objects 221 

Treatment of copper and its alloys, German silver and brass ; Freeing 
from grease ; Pickling ; Rubbing ; Pickling in the preliminary 
pickle ; Amalgamating (quicking) ; Slinging wires. . . . 222 

Treatment of the objects while being silvered ; Amount of silver de- 
posited upon several grades of plated-ware manufactured by the 
William Rogers Manufacturing Co., of Hartford, Conn. ; Method of 
controlling the weight of the deposit ...... 223 , 

Roseleur's plating balance ......... 225 

Plating balance with resistance-board, voltmeter, and silver bath ; Treat- 
ment of articles which are to retain the crystalline dead white with 
which they come from the bath ....... 226 

Polishing the silvered articles ; Mode of executing the operation of 
burnishing . . . . . . . . . . .227 

Burnishing machines ; Ordinary silvering ; Practice of the Meriden 
Britannia Co.'s works at Meriden, Conn., with Britannia or white 
metal ............ 228 

With German silver or nickel articles ; Steel articles ; Methods in use 
in the William Rogers Manufacturing Co., Hartford, Conn., for pre- 
paring work for plating ; For cleansing steel cutlery ; Nickel silver 
(German silver) for spoons ........ 229 

Britannia metal (hollow ware) ; Rogers's striking solution ; Meriden 
Company's striking solution ; extra heavy coating of silver on the 
convex surfaces of spoons and forks ; Sectional plating . . . 230 
Stopping- off; Stopping-oflf varnish ; Silvering of iron ; Silvering by 
contact, by immersion, and cold silvering with paste ; Bath for sil- 
vering by contact with zinc . . . . . . . .231 

Baths for silvering by immersion . . . . . . .232 

Preparation of solution of sodium sulphide . . . . . 233 

Dr. Ebermayer's bath for immersion ...... 234 

Process for silvering articles, especially those composed of the various 
alloys of copper, without the use of a current ..... 235 

Process of coating hooks and eyes, pins, etc., with a thin film of silver 236 
Cold silvering with paste ; Composition of argentiferous pastes ; grain- 



ing 



237 



Preparations used for graining . . . . . . . .238 

Execution of graining ; Resist and its composition ...'■• . . 239 
Silvering of fine copper wire ; Incrustations with silver, gold, and other 
metals • 240 



CONTENTS. XIX 

PAGE 

Niel or nielled silvering ; preparation of the nielling .... 241 

Imitation of niel by electro-deposition ; Old (antique) silvering ; Oxi- 
dized silver . . . . . . . . . . . 242 

Yellow color on silvered articles ; Stripping silvered articles . . 243 
Determination of electro-deposited silvering ; Process for the determin- 
ation of genuine silvering used by custom-house officers in Germany 244 
Recovery of silver from old silver baths, etc.; Wet method; Reduc- 
tion of the chloride of silver by pure zinc ..... 245 

CHAPTER X. 



DEPOSITION OF GOLD. 



246 
24 7 
248 



Properties of gold ; General composition of the native metal 
Gold baths, their composition, preparation, and properties . 
Baths for cold gilding ....... 

Bath prepared with yellow prussiate of potash ; Gold bath for hot 

gilding . . . . . . . 

Formula? for hot gilding recommended by Conrad Taucher 
Preparation of gold baths with the assistance of the electric current 

Management of gold baths ....... 

Employment of platinum anodes for coloring the deposit ; Vats for 

gold baths ; Heating gold baths .... 
Execution of gilding ; Gilding without a battery . 
Apparatus for gilding without a battery ; Preparation of the articles 

for gilding ; Current-strength for gilding .... 
Gilding of hollow ware; Gilding in the cold bath 
Gilding with the hot bath ; Red gilding ..... 
Determination of the content of copper required for obtaining a beau 

tiful red gold ; Green gilding ; Rose-color gilding ; Dead gilding 

O ' CO? .CO' DO 

Methods for deadening the surface ; Dead gilding on zinc . 

Coloring of the gilding ; Preparation of gilder's wax . 

Incrustations with gold ; Gilding of metallic wire and gauze 

J. W. Spaeth's machine for gilding metallic wire and gauze 

Gold bath for gilding metallic wire and gauze ; Gilding by contact, by 
immersion, and by friction ; Baths for gilding by contact 

Preparation of solution of chloride of gold . 

Porcelain capsules for dissolving gold 

Preparation of matt for gilded articles 

Formula? for baths for gilding by dipping . 

Gilding of porcelain, glass, etc. .... 

Gilding by friction, or gilding with the rag, with the thumb, with the 
cork; Martin and Peyraud's method of gilding by friction . . 268 

Fire or mercury gilding ; Preparation of the amalgam of gold ; Appli- 
cation of the amalgam ......... 269 



249 

250 

251 

252 
253 

251 
255 
256 

257 
258 
259 
260 
261 

262 
263 
264 
265 
266 
267 



XX CONTENTS. 

PAGE 

Method of gilding which is a combination of fire-gilding with electro- 
deposition ........... 271 

Du Fresne's method of gilding ; Removing gold from gilded articles — 

"Stripping". .......... 272 

Determination of genuine gilding ....... 273 

Recovery of gold from gold baths ; The wet process ; Recovery of gold 
from acid mixtures . . . . . . . .274 

CHAPTER XL 

DEPOSITION OF PLATINUM AND PALLADIUM. 

1. Deposition of Platinum. 

Properties of platinum ; Platinum baths, their composition, preparation, 
and properties ; Bottger's platinum bath ..... 275 

Preparation of platoso-ammonium chloride ; Platinum bath patented 
by the Bright Platinum Company, of London ; Directions for pre- 
paring platinum baths, by Dr. W. H. Wahl ; Alkaline platinate bath 276 
Preparation of an oxalate solution ....... 277 

Preparation of the phosphate bath ; Management of platinum baths . 278 
Execution of platinizing ; Platinizing of large objects ; Production of 
heavy deposits .......... 279 

Platinizing of glass ; Platinizing by contact ; Recovery of platinum 
fi'om platinum solutions ........ 280 

2. Deposition of Palladium. 

Properties of palladium ; Palladium bath according to M. Bertrand ; 
Palladium bath for plating watch movements according to M. Pilet 281 

CHAPTER XII. 

DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 

1. Deposition of Tin. 

Properties of tin ; Moiie metallique on tin ; Tin baths, their composition, 
preparation, and properties ; Direct tinning of objects of zinc, copper, 
and brass ; Previous coppering or preliminary tinning of iron and 
steel . 282 

Anodes used ; Alkaline tin bath ; Experiments with Salzede's bronze 
bath 283 

Pfanhauser's recent experiments ; Tin bath given by Taucher . . 284 

Management of tin baths ; Current-strength required ; Anodes ; Choice 
of tin-salt ; Refreshing the tin bath ; Execution of tinning . . 285 

Tinning by contact and boiling ; Solutions for tinning by contact ; 
Formula for tinning by immersion ; Zilken's patented solution for 



CONTENTS. XXI 

PAGE 

tinning by contact in a cold bath ; Tinning solution for iron and steel 

articles . . . . . . . . . . 286 

Tinning solution for small brass and copper articles ; Bottger's solution ; 

Eisner's bath ; Durable coating of tin . . . . . ■ . 287 
Tinning of needles ; Superficial coat of tin to articles of brass, copper, 

or iron; Stolba's method of tinning ...... 288 

2. Deposition of Zinc. 

Properties of zinc ; Zinc baths, their composition, preparation, and 
properties . . . . . . . . . . . 289 

Anodes used ; Execution of zincking ...... 290 

Zincking iron by contact ; To coat brass and copper with a bright layer 
of zinc ; Zinc alloys ; Production of an alloy of zinc and tin by the 
use of the battery . . . . . . . . . 291 

Suitable bath for the purpose . . . . . . , . 292 

3. Deposition of Lead. 

Properties of lead ; Lead baths, their composition, preparation, and 
properties ; Anodes ; To coat gun-barrels, and other articles of steel 
or iron with superoxide of lead ; Leading by contact . . .292 

Nobili's rings (iridescent colors, electrochromy) .... 293 

4. Deposition of Iron (Steeling). 

Principal use of the electro-deposition of iron ; Steel baths, their com- 
position, preparation, and properties ; Varrentrapp's steel bath . 293 

Baths for the production of electrotypes in iron ; Steel bath recom- 
mended by Klein ; C. Obernetter's method of steeling copper print- 
ing-plates . . . . . . . . . . . 294 

Production of a deep black deposit of iron for decorative purposes . 295 

Management of iron baths ; Execution of steeling ; Steeling by contact 296 

CHAPTER XIII. 

deposition of antimony, arsenic, and aluminium. 

1. Deposition of Antimony. 

Properties of antimony ; Antimony baths, their composition, prepara- 
tion, and properties ; Explosive property of the antimony deposit ; 
Lustrous non-explosive deposit of antimony ..... 297 

2. Deposition of Arsenic. 

Properties of arsenic ; Arsenic baths, their composition, preparation, 
and properties .......... 298 

Deposits of antimony and arsenic by contact and immersion . . 299 



XXU CONTENTS. 

3. Deposition of Aluminium. 

page 
Properties of aluminium 299 

Aluminium baths, their composition, preparation, an d properties ; Ber- 
trand's process ; Goze's process ; Herman Reinbold's formula ; New 
method for the electro-deposition of aluminium .... 300 

CHAPTER XIV. 

GALVANOPLASTY (REPRODUCTION). 

What is understood by galvanoplasty ; Copper the most suitable metal 
for galvanoplastic processes ........ 301 

Physical properties of copper deposited by electrolysis ; Smee's experi- 
ments ; Von Hiibl's experiments for the determination of the 
conditions under which deposits with different physical properties 
are obtained ; Classes of processes used in galvanoplasty . . 302 

1. Galvanoplastic Deposition in the Cell- Apparatus. 

The cell-apparatus . . . . . . . . . .303 

Simple apparatus for amateurs; Cell-apparatus used in printing estab- 
lishments for the production of cliches ...... 304 

Large apparatus ; French form of cell-apparatus .... 305 

German form of cell-apparatus . . . . . . . . 306 

Copper bath for the cell- apparatus ; Table giving the approximate con- 
tent of pure crystallized blue vitriol at different degrees B6., and at 

59° F 307 

Method of removing an excess of acid from the bath .... 308 

2. Galvanoplastic Deposition by the Battery and Dynamo-Machine. 

Arrangement for the employment of external sources of current . 308 

Depositions with the battery ; Use of the, Daniell and of Bunsen ele- 
ments ; Coupling of elements ; Depositions with dynamo-machines ; 
Best dynamo to use ......... 309 

Copper baths for galvanoplastic depositions with a separate source of 
current ; Bath for depositing with the dynamo ; Bath for depositing 
with the battery ; v. Hiibl's observations on the elasticity, strength, 
and hardness of galvanoplastic deposits of copper; Most suitable 
composition for copper printing-plates . . . . . .310 

Current-densities for baths at rest and in motion ; Disadvantage of the 
difference in composition of the upper and lower layers of the bath . 311 

Various methods of effecting the motion of the bath . . . .312 

Anodes used and their surface in proportion to that of the cathodes ; 
Determination of free acid ........ 313 

Determination of the content of copper according to Haen . . . 314 



CONTEXTS. XX111 



Preparation of moulds (matrices) in plastic material ; Suitable materials 
for this purpose ; Moulding in gutta-percha . . . . .315 

The toggle press . . . . . . . . . .316 

Hydraulic press ; Moulding in wax (stearine) . . . .317 

Various wax mixtures ; Preparation of the wax mould . . . 318 

Black-leading and machines used for the purpose ; Silas P. Knight's 
process of black-leading . . . . . . . . .319 

Preliminary coating of the black-leaded surface with copper . .320 

Gilt and silvered black-lead ; Wiring the mould ..... 321 

Method of providing as much metallic surface as possible ; The "elec- 
tric connection gripper;" Suspension of the moulds in the bath . 322 
Chief requisite for the production of a dense, coherent, and elastic de- 
posit ; Strength of the sulphuric acid for filling the clay cells . . 323 
Most suitable current-density for the production of a good deposit; 
Coupling of the elements ; Controlling the current by the resistance- 
board ; Time required for a sufficiently heavy deposit . . .324 
Accumulators and their use ........ 325 

Detaching the deposit from the mould ; Backing the deposit or shell . 326 
Composition for backing metal ; Finishing ; The saw table ; Types of 
power planing or shaving machines . . . . . . . 327 

Mounting the plates ; Bookplates ....... 328 

Process of making a copy directly from a metallic surface without the 
interposition of wax or gutta-percha . . . . . .329 

Electro-etching . . . . . . . . ' . . . 330 

Composition for etching ground . . . . . . . .331 

Preparation of printing-plates in relief; Heliography ; Heliographic 

process invented by Pretsch and improved by Scamoni . . . 332 

Galvanoplastic reproduction of busts, vases, etc. ; Materials for the 

moulds 333 

Moulding undercut reliefs and especially round plastic objects ; Dissec- 
tion of objects ; Moulding round articles in gutta-percha . . . 334 
Metallic alloys for the preparation of moulds ; Taking casts from metallic 
coins and medals in plaster of Paris ...... 335 

Casts from large plastic objects with undercut surfaces and reliefs in 
plaster of Paris . . . . . . . . . . 336 

Making plaster- of-Paris moulds impervious to fluids . . . .337 

Making the moulds conductive ; Metallization by the wet way . . -338 
Parkes's and various other methods of metallization by the wet way . 339 
Metallization by metallic powders ; Lenoir's process — Galvanoplastic 
method for originals in high relief ....... 340 

Gelatine moulds and their preparation ; Brandley's directions for pre- 
paring gelatine moulds .......... 341 

Special uses of galvanoplasty ; Nature printing; Philipp's process for 
coating laces and tissues with copper and then silvering or gilding ; 
Corvin's niello 342 



XXIV CONTENTS. 

PAGE 

Coating grasses, leaves, flowers, etc., with copper and then silvering, 
gilding, or platinizing ; Plates for the production of imitations of 
leather 343 

To coat wood, etc., with a galvanoplastic deposit of copper; To pro- 
tect wooden handles of surgical instruments, etc., from the attacks 
of the acid copper bath ; Copper deposit for the mercury vessels of 
thermometers ; Metallization of glass, porcelain, clay, terra cotta, 
etc. ; Galvanoplastic operations in iron ; Conditions for obtaining an 
any way successful iron electrotype . . . . . .344 

Galvanoplastic operations in nickel ....... 345 

Procedure for obtaining a deposit of nickel ; Galvanoplastic operations 
in silver and gold .......... 346 

Bath for galvanoplastic operations with silver ; Bath for galvanoplastic 
operations with gold . . . . . . . . .347 

CHAPTER XV. 

COLORING, PATINIZING, OXIDIZING, ETC., OF METALS.— LACQUERING. 

What is understood by patina and patinizing; Coloring of copper; 

Shades from the pale- red of copper to a dark chestnut-brown . .347 
Brown color upon copper ; Method used in the Paris mint ; Red-brown 

color on copper . . . . . . . . . . 348 

To color copper blue-black ; Black color upon copper ; Dead black on 

copper; Imitation of genuine patina ...... 349 

Steel-gray upon copper ; Dark steel-gray upon copper ; Various colors 

upon massive copper, brass, and nickel ...... 350 

Coloring of brass and bronze ; Lustrous black on brass ; steel-gray on 

brass ............ 351 

Gray color with a bluish tint on brass ; Straw color, to brown, through 

golden-yellow, and tombac color on brass; Color resembling gold on 

brass; Brown color, called bronze Barbedienne, on brass . . 352 

Coloring bronze articles dead yellow or clay yellow to dark brown ; 

Violet and corn-flower blue upon brass ; Ebermayer's experiments 

in coloring brass . . . . . . . . . . 353 

Coloring zinc ; Experiments in coloring zinc black ; Dullas's process ; 

Puscher's method; Neumann's process; Blue-black on zinc; Gray 

coating on zinc ; Bronzing on zinc ...... 355 

Bed-brown color on zinc ; Yellow-brown shades on zinc ; Coloring of 

iron ; Lustrous black on iron ; Meritens' process ; Durable blue on iron 

and steel ; Brown-black coating with bronze lustre on iron . . 356 
To give iron a silvery appearance with high lustre.; Coloring of tin ; 

Bronze-like patina on tin ; Durable and very warm sepia-brown tone 

upon tin and its alloys ; Dark coloration on tin ; Coloring of silver ; 

Lacquering ; Use of lacquers jn the, electro- plating industry . .357 



CONTEXTS. XXV 

PAGE 

Application of lacquer; Cellulose lacquers and varnishes; Zapon ; 

Kristaline . . . . . . • • ... 358 

Closet or drying rack ; Preparation of a lacquer similar to zapon or 

kristaline ' 359 

Operations of gold varnishers ; Varnishes at the disposal of gold var- 

nishers . . . . . . . . . • • < 360 

Resinous substances and tinctorial matters used in the manufacture of 

varnish; Removal of varnish from imperfectly varnished objects ;... 361 

CHAPTER XVI. 

HYGIENIC RULES FOR THE WORKSHOP. 

Neutralization of the action of acid upon the enamel of the teeth and 
the mucous membranes of the mouth and throat ; Protection against 
the corrosive effect of lime and caustic lyes ; Vessels used in the 
establishment not to be used for drinking purposes ; Precautions in 
handling potassium cyanide and its solutions ; Sensitiveness of many 
persons to nickel solutions . . . . . . . .362 

Poisoning by hydrocyanic (prussic) acid, potassium cyanide, or cyan- 
ides ; Remedies to be applied ; Poisoning by copper salts, by lead salts, 
and by arsenic .......... 363 

Poisoning by alkalies, by mercury salts, by sulphuretted hydrogen, by 
chlorine, sulphurous acid, nitrous and hyponitric gases . . . 364 

CHAPTER XVII. 

CHEMICAL PRODUCTS AND VARIOUS APPARATUS AND INSTRUMENTS 
USED IN ELECTRO-PLATING. 

A. Chemical Products. 
1. Acids. 

Sulphuric acid (oil of vitriol) and its recognition .... 365 

Nitric: acid (aqua fortis, spirit of nitre) and its recognition ; Hydro- 
chloric acid (muriatic acid) and its recognition ; Hydrocyanic acid 
(prussic acid) and its recognition . . . . . . . 366 

Citric acid and its recognition ; Boric acid (boracic acid) and its recogni- 
tion ; Arsenious acid (white arsenic, arsenic, ratsbane) and its 
recognition . . . . . . . . . . .367 

Chromic acid and its recognition ....... 368 

II. Alkalies and Alkaline Earths. 

Potassium hydrate (caustic potash) ....... 368 

Sodium hydrate (caustic soda) ; Ammonium hydrate (ammonia or 
spirits of hartshorn) and its recognition ; Calcium hydrate (burnt or 
quick lime) ........... 369 



XXVI CONTENTS. 

III. Sulphur Combinations. 

PAGE 

Sulphuretted hydrogen (sulphydric acid, hydrosulphuric acid) and its 
recognition ........... 369 

Potassium sulphide (liver of sulphur) and its recognition ; Ammonium 
sulphide (sulphydrate or hydrosulphate of ammonia) ; Carbon disul- 
phide or bisulphide ; Antimony sulphide ; Black sulphide of anti- 
mony (stibium sulfuratum nigrum) . . . . . .370 

Red sulphide of antimony (stibium sulfuratum aurantiacum) ; Arsenic 
trisulphide or arsenious sulphide (orpiment) ; Ferric sulphide . . 371 

IV. Chlorine Combinations. 

Sodium chloride (common salt, rock salt) and its recognition ; Ammo- 
nium chloride (sal ammoniac) and its recognition . . . .371 

Antimony trichloride (butter of antimony) ; Arsenious chloride ; Tin 
chloride; Stannous chloride (or tin salt) and its recognition; Stannic 
chloride ; Zinc chloride (hydrochlorate or muriate of zinc, butter of 
zinc) and its recognition . . . . . . . .372 

Zinc chloride and ammonium chloride ; Nickel chloride and its recog- 
nition ; Cobalt chloride and its recognition ; Silver chloride (horn 
silver) and its recognition ........ 373 

Gold chloride (terchloride of gold, muriate of gold, auric chloride) and 
its recognition ; Platinic chloride and its recognition . . .374 

V. Cyanides. 

Potassium cyanide (white prussiate of potash) and its recognition . 375 
Comparative table of potassium cyanide with a different content; Cop- 
per cyanides and their recognition ; Zinc cyanide (hydrocyanate of 
zinc, prussiate of zinc) and its recognition , . . . .376 
Silver cyanide (prussiate or hydrocyanate of silver) ; Potassium ferro- 
cyanide (yellow prussiate of potash) and its recognition . . .377 

VI. Carbonates. 

Potassium carbonate (potash) and its recognition . . . .377 

Acid potassium carbonate or monopotassic carbonate, commonly called 
bicarbonate of potash ; Sodium carbonate (washing-soda) ; Sodium 
bicarbonate (baking-soda) ; Calcium carbonate (marble, chalk) ; 

Whiting 378 

Copper carbonate and its recognition ; Zinc carbonate and its recogni- 
tion ; Nickel carbonate and its recognition ; Cobalt carbonate . .379 

VII. Sulphates and Sulphites. 

Sodium sulphate (Glauber's salt) ....... 379 

Ammonium sulphate and its recognition ; Aluminium-potassium sul- 
phate (potash-alum) and its recognition ; Ammonium-alum and its 



CONTENTS. XXV11 

PAGE 

recognition ; Iron sulphate (iron protosulphate, ferrous sulphate, or 
green vitriol) and its recognition ....... 380 

Iron-ammonium sulphate ; Copper sulphate (cupric sulphate or blue 
vitriol) and its recognition ; Zinc sulphate (white vitriol) and its re- 
cognition ........... 381 

Nickel sulphate and its recognition ; Nickel-ammonium sulphate ; Co- 
balt sulphate and its recognition ; Cobalt-ammonium sulphate ; So- 
dium sulphite and bisulphite ; Sodium sulphite and its recognition . 382 

Sodium bisulphite .......... 383 

VIII. Nitrates. 

Potassium nitrate (saltpetre, nitre) and its recognition ; Sodium nitrate 
(cubic nitre or Chile saltpetre) ; Mercurous nitrate . 383 

Mercuric nitrate and its recognition ; Silver nitrate (lunar caustic) and 
its recognition . . . . . . . . . . 384 

IX. Phosphates and Pyrophosphates. 

Sodium phosphate and its recognition ; Sodium pyrophosphate and its 
recognition; Ammonium phosphate . . . . . 385 

X. Salts of the Organic Acids. 

Potassium bitartrate (cream of tartar) ; Potassium-sodium tartrate 
(Rochelle or Seignette salt) and its recognition .... 385 

Antimony-potassium tartrate (tartar emetic) and its recognition ; Cop- 
per acetate (verdigris) ; Lead acetate (sugar of lead) and its recog- 
nition .... 386 

Sodium citrate . . ........ 387 

B. Various Apparatus and Instruments. 

Glass balloons and flasks ; Evaporating dishes or capsules ; Glass jars ; 
Crucibles 387 

Hydrometers; Twaddell's hydrometers . . . . . . 388 

Baume's hydrometers; Table showing readings of different hydrome- 
ters ; Filters . . . . . 389 

Siphons : Stirring rods . . . . . . . . .391 

CHAPTER XVIII. 

USEFUL TABLES. 

Table of elements, with their symbols, atomic weights, and specific 
gravities . . . . . . . . . . .393 

Table of chemical and electro-chemical equivalents ; Explanation of 
the table 394 



XX VIU CONTENTS. 

PAGE 

Table showing the value of equal current volumes as expressed in am- 
peres per square decimetre, per square foot, and per square inch of 
electrode surface ; Application of the table . . . . .395 

Table showing the specific electrical resistances of different sulphuric 
acid solutions at various temperatures (Fleeming Jenkin) ; Table 
showing the specific electrical resistances of different copper sulphate 
solutions at various temperatures (Fleeming Jenkin) ; Definition of 
specific resistance . . . . " . . . '. . . 396 

Table of the electro-motive force of elements ... . . . 397 

Table showing the solubility of various substances ; Table showing the 
composition of the most usual alloys and solders .... 398 

Alloys ............. 399 

Solders ; Soft solder ; Hard solder ; Silver solder .... 400 

Gold solder; Table of the melting-points of some metals; Table of 
high temperatures ; Table of the specific gravity and content of solu- 
tions of potassium carbonate at 57.2° F., according to Gerlach . 401 

Table showing the specific gravity of sulphuric acid at 59° F., accord- 
ing to Kolb . 402 

Table of the specific gravity and content of nitric acid, according to 
Kolb ; Table showing the specific gravity of sal ammoniac solutions 
at 66.2° F., according to Setoff" . . . . . . .403 

Table showing the electrical resistance of pure copper wire of various 
diameters ; Resistance and conductivity of pure copper at different 
temperatures .......... 404 

Table showing actual diameters in decimal parts of an inch correspond- 
ing to the numbers of various wire gauges . . • . . . 405 

Weight of iron, copper, and brass wire and plates .... 406 

Rules for speed ; To find speed of countershaft in accordance with 
main shaft and machine ; To find diameter of pulley on the main 
shaft ; To find diameter of pulley on countershaft carrying belt to 
machine; To find the speed of a machine . . . . .407 

Comparison of the scales of the Fahrenheit, Centigrade, and Reau- 
mur thermometers, and rules for converting one scale into another 408 

Index . 409 



ELECTRO-DEPOSITION OF METALS. 



i. 

HISTOEICAL PAET. 



CHAPTER I. 

HISTORICAL REVIEW OF ELECTRO-METALLURGY. 

In reviewing the history of the development of electrolysis, 
i. e., the reduction of a metal or a metallic alloy from the solu- 
tion of its salts by the electric current, the simple reduction which 
takes place by the immersion of one metal in the solution of 
another, may be omitted. This mode of reduction was well 
known to the alchemist Zozimus, who described the reduction of 
copper from its solutions by means of iron, while Paracelsus 
speaks of coating copper and iron with silver by simple immer- 
sion in a solution of silver. 

Before the discovery, in 1789, of contact-electricity by Luigi 
Galvani, there was nothing like a scientific reduction of metal 
by electricity; and only in 1799 did Alexander Volta, of Pa via, 
succeed in finding the true causes of Galvani's discovery. 
Galvani observed while dissecting a frog on a table, whereon 
stood an electric machine, that the limbs suddenly became con- 
vulsed by one of his pupils touching the crural nerve with the 
dissecting-knife at the instant of taking a spark from the con- 
ductor of the machine. The experiment was repeated several 
times, and it was found to answer in all cases when a metallic 
conductor was connected with the nerve, but not otherwise. He 
observed that muscular contractions were produced by forming a 
connection between two different metals, one of which was applied 
l 



'A ELECTKO-DEPOSITION OF METALS. 

to the nerve, and the other to the muscles of the leg. Similar 
phenomena having been found to arise when the leg of the frog 
Avas connected with the electric machine, it could scarcely be 
doubted that in both cases the muscular contractions were pro- 
duced by the same agent. From a course of experiments, Gal- 
vani drew the erroneous inference that these muscular contrac- 
tions were caused by a fluid having its seat in the nerves, which 
through the metallic connections flowed over upon the muscles. 
Everywhere, in Germany, England, and France, eminent scien- 
tists hastened to repeat Galvani's experiments in the hope of dis- 
covering in the organism a fluid which they considered the vital 
principle ; but it was reserved to Volta to throw light upon the 
prevailing darkness. In his repeated experiments this eminent 
philosopher observed that one circumstance had been entirely 
overlooked, namely, that in order to produce strong muscular 
contractions in the frog-leg experiment it was absolutely neces- 
sary for the metallic connection to consist of two different metals 
coming in contact with each other. From this he drew the infer- 
ence that the agent producing the muscular contractions was not 
a nerve-fluid, but was developed by the contact of dissimilar 
metals, and identical with the electricity of the electric machine. 

This discovery led to the construction of what is known as 
the pile of Volta, or the voltaic pile. The same philosopher found 
that the development of electricity could be increased by build- 
ing up in regular order a pile of pairs of plates of dissimilar 
metals, each pair being separated on either side from the adjacent 
pairs by pieces of moistened card-board or felt. On account of 
various defects of the voltaic pile, Cruikshank soon afterwards 
devised his well-known trough battery, which consisted of square 
plates of copper and zinc soldered together, and so arranged and 
fastened in parallel order in a wooden box, that between each 
pair of plates a sort of trough was formed, which was filled with 
acidulated water. 

Nicholson and Carlisle, on May 2, 1800, first decomposed 
water into hydrogen and oxygen by electrolysis ; and, in 1801, 
Wollaston remarked that if a piece of silver in connection with 
a more positive metal, for instance, zinc, be put into a solution of 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 3 

copper, the silver will be coated over with copper, which coating 
will stand the operation of burnishing. 

Cruikshank, in 1803, investigated the behavior of solutions of 
nitrate of silver, sulphate of copper, acetate of lead, and several 
other metallic salts, towards the galvanic current, and found that 
the metals were so completely reduced from their solutions by the 
current as to suggest to him the analysis of minerals by means of 
the voltaic current. 

To Brugnatelli we owe the first practical results in electro-gild- 
ing. In 1805, he gilded two silver medals by connecting them 
by means of copper wire with the negative pole of the pile, and 
allowing them to dip in a solution of fulminating gold in potas- 
sium cyanide, while a piece of metal was suspended in the solu- 
tion from the positive pole. He also observed that the positive 
plate, if it consisted of an oxidizable metal, was dissolved. 

One of the greatest discoveries connected with the subject, how- 
ever, is that of Sir Humphry Davy, made October 6, 1807, when, 
by the decomposition of the alkalies by means of the electric cur*, 
rent, he discovered the metals potassium and sodium. 

Prof. Oersted, of Copenhagen, in 1820, found that the mag- 
netic needle is deflected from its direction by the electric current. 
It was known long before this that powerful electric discharges 
affect the magnetic needle; it had, for instance, been observed 
that the needle of a ship's compass struck by lightning had lost 
its property of indicating the North Pole, and several physicists, 
among them Franklin, had succeeded in producing the same 
phenomena by heavy discharges of the electrical machine, but 
they were satisfied with the supposition that the electric current 
acted mechanically, like the blow of a hammer. Oersted first 
perceived that electricity must be in a state of motion in order to 
act upon magnetism. This led to the construction of the gal- 
vanoscope or galvanometer, an instrument which indicates whether 
the elements or other source of current furnish a current or not, 
and by which the intensity of the source of current may also to 
a certain degree be recognized. 

Ohm, in 1827, discovered the law named after him, that the 
strength of a continuous current is directly proportional to the dif- 
ference of potential or electro-motive force in the circuit, and inversely 



4 ELECTEO-DEPOSITION OF METALS. 

'proportional to the resistance of the circuit. This law will be more 
fully discussed in the theoretical part. 

Ohm's discovery was succeeded, in 1831, by the important dis- 
covery of electric induction by Faraday. By induction is under- 
stood the production of an electric current in a closed circuit 
which is in the immediate neighborhood of a current-carrying 
wire. Faraday further found that the current induced in the 
neighboring wire is not constant, because, after a few oscillations 
the magnetic needle returned to the position occupied by it before 
a current was passed through the current-carrying wire ; whilst 
when the current was broken the needle deflected in the opposite 
direction. 

In the year following the discovery of Faraday, Pixii, of Paris, 
constructed the first electro-magnetic induction machine. 

Faraday's electrolytic law of the proportionality of the current- 
strength and its chemical action, and that the quantities of the 
various substances which are reduced from their combinations by 
the same current are proportional to their chemical equivalents, 
was laid down and proved in 1833, and upon this Faraday based 
the measurement of the current-strength by chemical deposition, 
as, for instance, that of water, in the voltameter. 

Of the practical electro-chemical discoveries there remain to 
be mentioned the production of iridescent colors, in 1826, by 
Nobili, and the production of the amalgams of potassium and 
sodium, in 1835, by Bird. 

The actual galvanoplastic process, however, dates from the year 
1838. In the spring of 1838, Prof. Jacoby announced to the 
Academy of Sciences of St. Petersburg, a description of his dis- 
covery of the utility of galvanic electricity as a means of repro- 
ducing objects of metal. Hence Jacoby must be considered the 
father of galvanoplasty in as far as he was the first to utilize and 
give practical form to the discoveries made up to that time. 
Though Jacoby's process was published in the English periodical, 
"The Athenaeum," of May 4, 1839, Mr. T. Spencer, who read a 
paper on the same subject, Sept. 13, 1 839, before the Liverpool 
Polytechnic Society, claimed priority of invention, as was also 
done by Mr. C. J. Jordan, who, in May 22, 1839, sent a letter to 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 5 

the "London Mechanical Magazine/' which was published on 
June 8, 1839. 

From this time forward the galvanoplastic art made rapid 
progress, and by the skill and enterprise of such men as the 
Elkingtons, of Birmingham, and De Ruolz, of Paris, it was 
speedily added to the industrial arts. 

Though copies of a metallic object by means of galvanoplasty 
could now be made, the employment of the process was restricted 
to metallic objects of a form suitable for the purpose, until, in 
1840, Murray succeeded in making non-metallic surfaces conduc- 
tive by the application of graphite (black lead, plumbago), which 
rendered the production of galvanoplastic copies of wood-cuts, 
plaster-of-Paris casts, etc., possible. 

Dr. Montgomery, in 1843, sent to England samples of gutta- 
percha, which was soon found to be a suitable material for the 
production of negatives of the original models to be reproduced 
by galvanoplasty. 

Though it was now understood how to produce heavy deposits 
of copper, those of gold and silver could only be obtained in 
very thin layers. Scheele's observations on the solubility of the 
cyanide combinations of gold and silver in potassium cyanide, led 
Wright, a co-worker of the Elkingtons, to employ, in 1840, such 
solutions for the deposition of gold and silver, and it was found 
that deposits produced from these solutions could be developed to 
any desired thickness. The use of solutions of metallic cyanides 
in potassium cyanide prevails at the present time, and the results 
obtained thereby have not been surpassed. 

From the same year also dates the patent for the deposition of 
nickel from solution of nitrate of nickel, without, however, at- 
tracting any special attention, which may have been chiefly due 
to the fact that the deposition of nickel from its nitrate solution 
is the most imperfect and the least suitable for the practice. 

To Mr. Alfred Smee we owe many discoveries in the deposition 
of antimony, platinum, gold, silver, iron, lead, copper, and zinc. 
In publishing his experiments, in 1841, he originated the very 
appropriate term " electro-metallurgy" for the process of working 
in metals by means of electrolysis. 

Prof. Boettger, in 1842, pointed out that dense and lustrous 



G ELECTKO-DEPOSITION OF METALS. 

depositions of nickel could be obtained from its double salt, sul- 
phate of nickel with sulphate of ammonium, as well as from 
ammoniacal solution of sulphate of nickel ; and that such de- 
posits, on account of their slight oxidability, great hardness, and 
elegant appearance were capable of many applications. Boettger's 
statements also fell into oblivion, and only in later years when 
the execution of nickeling was practically taken up in the United 
States, his labors in this department were remembered in Ger- 
many. To Boettger we are also indebted for directions for coat- 
iug metals with iron, cobalt, platinum, and various patinas. 

In the same year, De Ruolz first succeeded in depositing metal- 
lic alloys — for instance, brass — from the solutions of the mixed 
metallic salts. In 1843 the first use of thermo-electricity appears 
to have been made by Moses Poole, who took out a patent for 
the use of a thermo-electric pile instead of a volatic battery for 
depositing purposes. 

From this time forward innumerable improvements in existing 
processes were made ; and also the first endeavors to apply Fara- 
day's discoveries to practical purposes 

The invention of depositing metals by means of a permanent 
current of electricity obtained from steel magnets was perfected 
and first successfully worked by Messrs. Prime & Son, at their 
large silverware works, Birmingham, England, and the original 
machine, constructed by Woolrych in 1844 — the first magnetic 
machine that ever deposited silver on a practical scale — is still 
preserved at their works in its original position as a valuable and 
interesting relic. The Woolrych machine stands 5 feet high, 5 
feet long, and 2J feet wide. An illustration of this original 
electro-plating machine, kindly furnished us by the Hanson & 
Van Winkle Co. of Newark, N. J., is given in Fig. 1. 

As early as 1854, Christofle & Co. endeavored to replace their 
batteries by magneto-electrical machines, and used the Holmes 
type, better known as the Alliance Machine, which, however, did 
not prove satisfactory ; and besides, the prices of these machines 
were in comparison with their efficacy exorbitant. The machine 
constructed by Wilde proved objectionable on account of its heat- 
ing while working, and the consequent frequent interruptions in 
the operations. 



HISTORICAL REVIEW OP ELECTRO-METALLURGY. 7 

In 1860 Dr. Antonie Pacinotti, of Pisa, suggested the use ot 
an iron ring wound round with insulated wire, in place of the 
cylinder. This ring, named after its inventor, has, with more or 
less modifications, become typical of many machines of modern 

Fig. 1. 




construction. In the construction of all older machines, steel 
magnets had been used, and their magnetism not being constant, 
the effect of the machine was consequently also not constant. 
Furthermore, they generated alternately negative and positive 
currents, which, by means of commutators, had to be converted 
into currents of the same direction ; and this, in consequence of 
the vigorous formation of sparks, caused the rapid wearing out of 
the commutators. 

These defects led to the employment of continuous magnetism 
in the iron cores of the electro-magnets, the first machine based 
upon this being introduced in 1866, by Siemens, which, in 1867, 
•was succeeded by Wheatstone's. 



8 ELECTRO-DEPOSITION OF METALS. 

However, the first useful machine was introduced in 1871, by 
Zenobe Gramme, who in its construction made use of Pacinotti's 
ring. This machine was, in 1872, succeeded by Hefner-Alteneck's, 
of Berlin. In both machines the poles of the electro-magnet 
exert an inducing action only upon the outer wire wrappings of 
the revolving ring, the other portions being scarcely utilized, 
which increases the resistance and causes a useless production of 
heat. This defect lead to the construction of flat-ring machines, 
in which the cylindrical ring is replaced by one of a flat shape, 
and of larger diameter, thus permitting the induction of both flat 
sides. Such a machine was, in 1884, built by Siemens & Halske, 
of Berlin • and in the same year by S. Schuckert, of JSTiirenberg. 
In Schuckert's modern machines nearly three-quarters of all the 
wire wrappings are under the inducing influence of both of the 
large pole shoes of the electro-magnets. 

Of other constructions of dynamo-electrical machines may be 
mentioned Mather's, Elmore's, Fein's, Mohring's, Krottlinger's, 
and Lahmeyer's, the latter especially being at the present time 
much employed in Germany for electro-plating purposes. In this 
country Weston's machine and the dynamos manufactured by the 
Hanson & Van Winkle Co., of Newark, N. J., the Zucker & 
Levett Chemical Co., of New York, and others are largely used 
for electro-plating purposes. 

For the sake of completeness, there may be mentioned the in- 
vestigators and practitioners who during the last twenty years 
have contributed much to the improvement of the electro-chemi- 
cal processes and the perfection of galvanoplasty. Besides those 
already named, they are : Elkington, Becquerel, Heeren, Roseleur, 
Eisner, von Leuchtenberg, Meidinger, Weil, Goode, Christofle, 
Klein, von Kress, Thompson, Adams, GiafFe, and others. 



MAGNETISM AND ELECTRICITY. 



II. 

THEOEETICAL PART. 



CHAPTER II. 

magnetism and electricity. 

1. Magnetism. 

For the better understanding of the electrolytic laws it will be 
necessary to commence with the phenomena presented by magnet- 
ism, and to consider them more closely. 

A particular species of iron ore is remarkable for its property of 
attracting small pieces of iron and causing them to adhere to its 
surface. This iron ore is a combination of ferric oxide with fer- 
rous oxide (Fe 3 4 ), and is called loadstone or magnetic iron ore. 
Its properties were known to the ancients, who called it magnesian 
stone after Magnesia, a city in Thessaly, in the neighborhood of 
which it was found. If a natural loadstone be rubbed over a bar 
of steel, its characteristic properties will be communicated to the 
bar, which will then be found to attract iron filings like the load- 
stone itself. The bar of steel thus treated is said to be magnet- 
ized, or to constitute an artificial magnet. The artificial magnets 
thus produced may be straight, in the shape of a horseshoe, or 
annular ; but no matter what their form, the attractive force will 
appear to be greatest at two points situated near the extremities 
of the bar, and least of all toM^ards the middle. The points of 
the magnet showing the greatest attractive force are called the 
magnetic poles, whilst the line between them, possessing little or 
no attractive force, is termed the neutral line or neutral zone. In 
a closed magnet the poles are situated on the ends of one and the 
same diameter, while the neutral zones are located on the ends of 
a diameter standing perpendicular to the first. 



10 ELECTRO-DEPOSITION OF METALS. 

When a magnetized bar or natural magnet is suspended at its 
centre in any convenient manner, so as to be free to move in a 
horizontal plane, it is always found to assume a particular direc- 
tion with regard to the earth, one end pointing nearly north and 
the other nearly south. If the bar be removed from this position 
it will tend to reassume it, and, after a few oscillations, settle at 
rest as before. The direction of the magnetic bar, i. e., that of its 
longitudinal axis, is called the magnetic meridian, while the pole 
pointing towards the north is usually distinguished as the north 
pole of the bar, and that which points southward as the south pole. 

A magnet, either natural or artificial, of symmetrical form, 
suspended in the presence of a second magnet, serves to exhibit 
certain phenomena of attraction and repulsion, which deserve 
particular attention. When a north pole is presented to a south 
pole, or a south pole to a north, attraction ensues between them ; 
the ends of the bar approach each other, and, if permitted, adhere 
with considerable force ; when, on the other hand, a north pole is 
brought near a second north pole, or a south pole near another 
south pole, mutual repulsion is observed, and the ends of the bar 
recede from each other as far as possible. Poles of an opposite 
name attract, and, poles of a similar name repel each other. 

According to the theory or hypothesis proposed by Ampere 
magnetism is caused by the presence of electric currents in the 
ultimate particles of matter. This theory assumes — 

1. That the ultimate particles of all magnetizable bodies have 
closed electric circuits in which electric currents are continually 
flowing. 

2. That in an unmagnetized body these circuits neutralize one 
another, because they have different directions. 

3. That the act of magnetization consists in such a polarization 
of the particles as will cause these currents to flow in the one and 
the same direction, magnectic saturation being reached when all 
the separate circuits are parallel to one another. 

4. That coercive force is due to the resistance these circuits 
offer to a change in the direction of their planes. 

Guided by these considerations Ampere produced a coil of wire, 
called a solenoid, which is the equivalent of the magnetizing circuit 
assumed by his theory. It therefore follows that an electric cur- 



MAGNETISM AND ELECTRICITY. 11 

rent sent through a coil of insulated wire surrounding a rod or 
bar of soft iron, or other readily magnetizable material, will make 
the same a magnet. A magnet so produced is called an electro- 
magnet ; the magnetizing coil is called a helix, or solenoid. The 
polarity of the magnet depends on the direction of the current, or 
on the direction of winding of the helix or solenoid. The im- 
probability of an electric current continually flowing in a circuit 
without the expenditure of energy, has led many scientific men to 
reject Ampere's theory of magnetism. 

If an iron or steel needle be suspended free in the neighborhood 
of a magnet, it assumes a determined direction according to its 
greater or smaller distance from the poles or from the neutral 
zone ; however, before the needle assumes this direction it swings 
quickly, with a shorter stroke, or slowly with a longer stroke, 
according to the greater or smaller attractive force exerted upon 
it. The space within which the magnetic action of a magnet is 
exercised is called the magnetic field, and the magnetic as well as 
the electric attractions and repulsions are, according to Coulomb, 
as the densities of the fluids acting upon each other and inversely 
as the square of their distance. 

2. Electricity. 

In an ordinary state solid bodies exhibit no attractive effect 
upon small light particles, such as strips of paper, balls of elder- 
pith, etc ; but by rubbing many solid bodies with a piece of dry 
cloth or fur they acquire the property of attracting such light 
bodies as mentioned above. The cause of this phenomenon is 
called electricity, and the bodies which possess this property of 
becoming electric by friction are termed idio-electrics, and those 
which do not appear to possess it, non-electrics. Gray, in 1727, 
found that all non-electric bodies conduct electricity, and hence 
are conductors, while those which become electric by friction are 
non-conductors of electricity. Strictly speaking, there are no non- 
conductors, because the resins, silk, glass, etc., conduct electricity, 
though only very slightly. It is therefore better to distinguish 
good and bad conductors. To test whether a body belongs to 
the idio-electrics, the so-called electroscope is used, which in its 



12 ELECTRO-DEPOSITIOJST OF METALS. 

simplest form consists of a glass rod mounted on a stand, and 
bent at the top into a hook, from which hangs by a silken thread 
or hair a pith ball. If, on bringing the rubbed body near the 
pith ball, the latter is attracted, the body is electric, whilst if the 
ball is not attracted, the body is either non-electric or its elec- 
tricity is too slight to produce an attractive effect. 

From the following experiments it was found that there exist 
two kinds of electricity : When a rubbed rod of glass or shellac 
is brought near the ball of elder-pith suspended to a silk thread, 
the ball is attracted, touches the rod, adheres for a few moments 
and is then repulsed. This repulsion is due to the fact that the 
ball by coming in contact with the rod becomes itself electric, and 
its electricity must first be withdrawn by touching with the hand 
before it can again be attracted by the rod. By now taking two 
such balls, one of which has been made electric by touching with 
a glass rod, which -had been rubbed with silk, and the other by 
touching with a shellac rod rubbed with cloth, it will be observed 
that the ball, which is repulsed by the glass rod, is attracted by 
the shellac rod and vice versa. These two kinds of electricity are 
called vitreous or positive, and resinous or negative electricty, and 
it has been found that electricities of a similar name attract, and 
electricities of an opposite name repel, each other. 

For want of a concrete knowledge of the electric agent which 
produces the electric phenomena, various theories or hypotheses 
have been advanced to explain these phenomeua and the action 
of the electric forces. Only two of the best known theories or 
hypotheses shall here be mentioned. 

Double fluid hypothesis of electricity. By this hypothesis it is 
endeavored to explain the causes of electric phenomena by the 
assumption of the existence of two different electric fluids. 

The double fluid hypothesis assumes : — 

1. That the phenomena of electricity are due to two tenuous 
and imponderable fluids, the positive and the negative. 

2. That the particles of the positive fluid repel one another, as 
do also the particles of the negative fluid ; but that the particles 
of the positive fluid attract the particles of the negative, and vice 
versa. 



MAGNETISM AND ELECTRICITY. 13 

3. That the two fluids are strongly attracted by matter, and 
when present in it produce electrification. 

4. That the two fluids attract one another and unite, thus 
masking the properties of each. 

5. That the act of friction separates these fluids, one going to 
the rubber and the other to the thing rubbed. 

Single-fluid hypothesis of electricity. By this hypothesis it is 
endeavored to explain the cause of electric phenomena by the 
assumption of the existence of a single electric fluid. 

The single fluid hypothesis assumes : — 

1. That the phenomena of electricity are due to the presence 
of a single, tenuous, imponderable fluid. 

2. That the particles of this fluid mutually repel one another, 
but are attracted by all matter. 

3. That every substance possesses a definite capacity for hold- 
ing the assumed electric fluid, and that when this capacity is just 
satisfied, no effects of electrification are manifest. 

4. That when the body has less than this quantity present, it 
becomes negatively excited, and when it has more, positively excited. 

5. That the act of friction causes a redistribution of the fluid, 
part of it going to one of the bodies, giving it a surplus, thus 
positively electrifying it, and leaving the other with a deficit, 
thus negatively electrifying it. 

According to Coulomb, the electric attractions and repulsions 
are as the densities of the fluids acting upon each other, and in- 
versely as the square of the distance. 

However, a current of electricity is created not only by fric- 
tion, but also by the contact of various metals. In the same 
manner as the copper and iron in Galvani's experiments with the 
frog leg, other metals and conductors of electricity also become 
electric by contact, the electric charges being, however, stronger 
or weaker, according to the nature of the metals. If zinc be 
brought in contact with platinum, it becomes more strongly posi- 
tively electric than when in contact with copper ; whilst, how- 
ever, copper in contact with zinc is negatively excited, in contact 
with platinum it becomes positively electric. By now arranging 
the metals in a series, so that each preceding metal becomes posi- 
tively electric in contact with the succeeding, a series of electro- 



14 ELECTKO-DEPOSITION OF METALS. 

motive force or tension is obtained, in which the metals or con- 
ductors of electricity stand as follows : — 

+ Zinc, cadmium, tin, iron, lead, copper, nickel, 
Silver, antimony, gold, platinum, carbon — . 

While two metals of the series of electro-motive force or tension 
touching each other become electrically excited in such a manner 
that one becomes positively and the other negatively electric, an 
exchange of the opposite electricities takes place by introducing a 
conducting fluid between the metals. Thus, if a plate of zinc and 
a plate of copper connected by a metallic wire are immersed in a 
conducting fluid, for instance, dilute sulphuric acid, the electricity 
of the positive zinc passes through the fluid to the negative cop- 
per, and returns through the wire — the dosing circuit — to the 
zinc. However, in the same degree with which the electricities 
equalize themselves, new quantities of them are constantly formed 
on the points of contact of the metals with the conducting fluid ; 
and, hence, the flow of electricity is continuous. This electric 
current generated by the contact of metals and fluids is called 
the galvanic current ; or, since it is generated by the intervention 
of fluid conductors, hydro-electric current. A combination of 
conductors which yields such a galvanic current, is called a gal- 
vanic element, or a galvanic chain. 

It would here be the place to discuss the various galvanic ele- 
ments, but it is thought better to describe them in a separate 
chapter, and first to explain the laws and the actions of the gal- 
vanic current. 

Electrical potential. — The property of electricity corresponding 
to head or pressure, as applied in speaking of gas or water-power, 
is termed the electrical potential. Two bodies have the same elec- 
trical potential when, connected by a metallic wire, they develop 
no electricity. 

Electro-motive force. — If, however, two bodies connected by a 
metallic wire possess unequal electrical potentials, a movement 
of the electricity takes place, and the force which produces this 
movement or current is called the electro-motive force or tension. 
It, therefore, corresponds to the difference of the potentials ; and 



MAGNETISM AND ELECTRICITY 



15 



the magnitude of this difference of the potentials is the measure 
for the electro-motive force. 

Resistance. — All conductors offer a certain amount of resist- 
ance to the forward movement of the electric current. By con- 
necting, for instance, two bodies charged with electricity and 
possessing a difference of potentials, by a metallic conductor, a 
certain time is required for the compensation of the difference of 
potentials, or, in other words, before the electrical equilibrium is 
established. By now keeping the difference of potentials con- 
stant, the quantity of electricity which passes through the closing 
conductor — the closing circuit — depends on the resistance which 
the latter offers to the passage of the current. 

The resistance of a conductor is proportional to its length and 
inversely to its cross-section and its conducting capacity ; i. e., the 
longer the conducting circuit the greater the resistance, and the 
greater its cross-sections the smaller the resistance. Wires of 
small diameter will, therefore, offer greater resistance to the cur- 
rent than those with larger diameter, and wires with good con- 
ducting capacity will produce less resistance than those with poor 
conducting capacity. According to Lazere Weiler, the conduc- 
tivity of metals is as follows : — 



Name of metal. 


Mean 
conductivity. 


Alloys, etc. 


Mean 
conductivity. 


Silver .... 


100.0 


Cu with 4 per cent 


Si, 


75.0 


Copper 






100.0 


Cu " 12 


Si, 


54.7 


Goid 






80.6 


Cu " 9 " 


P, 


4.9 


Aluminium 






55.1 


Cu " 10 


Pb, 


30.0 


Zinc 






30 2 


Cu " 10 " 


Al, 


12.6 


Platinum 






16.7 


Cu " 10 " 


As, 


9.1 


Iron 






16.4 


Cu " 20 " 


Sn, 


8.4 


Tin 






15.2 


Cu " 35 


Zn, 


21.1 


Lead . 






8.8 


Cu " 50 " 


Ag, 


86.6 


Nickel 






7.9 


Au " 50 " 


A g, 


16.1 


Antimony- 






4.2 


Sn " 12 


Na, 


46.9 



Quantity of current. Ohm's law. — The quantity of electricity 
or, in other words, the current-strength, which an element fur- 
nishes at a determined extreme point, depends on the strength of 
the electro-motive force which impels the current, as well as on 
the resistance which the conductor offers to the current. In 



16 ELECTRO-DEPOSITION OF METALS. 

the preceding it has been seen that the electro-motive force corre- 
sponds to the difference of the potentials of two conductors con- 
nected by a metallic wire ; the greater this difference is, the greater 
the energy with which the compensation of the electricities takes 
place. It has also been explained that the resistance increases 
in proportion to the length, and decreases with the increase in 
the cross-section of the conductor. Upon these relations Ohm's 
law is based, and in its completeness it may be summed up as 
follows : The quantity of electricity or the strength (intensity) of 
current is directly proportional to the sum of the electro-motive forces 
of the exciting elements, and is inversely proportional to the sum of 
the resistances of its closing circuit ; however, the resistance of each 
part of the closing circuit is proportional to its length and inversely 
proportional to its cross-section. Now, if 8 indicates the strength 
of current, E the sum of the electro-motive forces, and L the 
total resistance, then the strength of current S is — 

9 E 

The total resistance L is, however, composed of two different 
resistances, namely, of the so-called essential or internal resistance, 
which expresses the resistance of the substances in the elements 
themselves, and of the non-essential or external resistance of the 
closing circuit. If, therefore, the internal resistance = R and the 
external resistance = r, the total resistance will be L = R + r, 
and the formula given above is changed to 

a_ E 
R + r 
Let us now examine the useful applications which result from 
Ohm's law, to the coupling of the elements, they being of great 
importance to the practical electro-plater. According to the 
above formula, which expresses the total performance of a bat- 
tery, the strength of current of a single element is, if s indicates 
its current strength, e the electro-motive force, R the essential 
or internal resistance, and r the resistance in the closing circuit, 



R + r 
By now uniting several such elements, let us say n elements, 
to a column, the electro-motive force of the latter has become 



MAGNETISM AND ELECTRICITY. 17 

n-\-e — ne, and the internal resistance nr; with the same closing- 
circuit as that of the single element, r will not increase, hence the 
strength of current of these n elements must be written — 

ne 
s = - 



n R + r 

It is now clear that when a deter-mined closing circuit of the 
resistance r is given that the strength of current cannot be indefi- 
nitely augmented by increasing the' number of n elements; 
because, though the electro-motive force, by the augmentation of 
n elements, increases by so many n, the internal resistance R also 
grows, so that finally the value r, which remains constant, dis- 
appears, contrary to the resistance R, which increases n times. 
Hence, the strength of current constantly approaches more the 
limit of value — 

ne e 
nR^R' 

On the other hand, the effect can neither be increased by 
enlarging the area of the pair of plates nor by decreasing the 
resistance of the fluid in a given number of elements. Because, 
when r, the external resistance, is sufficiently large so that the 
internal resistance, n R, may be neglected, the intensity always 

approaches more the value — • 

r 

Hence, it follows that the augmentation of the area of the ex- 
citing pair of plates produces an increase in the current-strength 
only when the external resistance in the closing circuit is small in 
proportion to the internal resistance of the battery. 

If we now apply the results of the above explanations to 
practice, we find that the elements may be coupled in various ways 
according to requirement. 

1. If, for instance, four Bunsen elements (carbon-zinc) are 
coupled one after another in such a manner that the zinc of 
one element is connected with the carbon of the next, and so on 
(Fig. 2), the current passes four times in succession through an 
equally large layer of fluid, in consequence of which the internal 
resistance, 4 R, is four times greater than that of a single element, 
while the resistance of the closing circuit, r, remains the same. 
2 



18 



ELECTRO-DEPOSITION OF METALS. 



Hence, while the current-strength is thereby not increased, the 
electro-motive force is, and for this reason this mode of coupling is 
called the union or coupling of the elements for electro-motive force 
or tension. 

Fig. 2. 

2. By connecting four elements alongside of each other, i. e., all 
the zinc plates and all the carbon plates one with another (Fig. 3), 

Fie. 3. 




Fig. 4. 



the current simultaneously passes through the same layer of fluid 
in four places ; the internal resistance of the battery is therefore 

the same as that of a single element, 
and since the area of the plates is 
four times larger than that of a single 
element, the quantity of current is 
augmented by this mode of coupling. 
This is called coupling for quantity of 
current. 

3. Two elements may, however, be 
connected for electro-motive force or 
tension, and several such groups 
coupled alongside of each other as 
v shown in Fig. 4, whereby, according 
to what has above been said, the electro- 
motive force as well as the current-strength is augmented. This 
mode of connection is called mixed coupling. 

According to the resistance of the bath as well as of the exte- 
rior closing circuit, and the surfaces to be plated, the electro-plater 
may couple his elements in either way, and in speaking later on 




MAGNETISM AND ELECTRICITY. 19 

of the elements the various modes of coupling will be further 
discussed. We will here only mention the proposition deduced 
from Ohm's law that a number of galvanic elements yield the 
maximum of intensity of current when they are so arranged that 
the internal resistance of the battery is equal to the resistance in the 
closing circuit. Hence, when operating with baths of good conduc- 
tivity and slight resistance, for instance, acid copper baths, silver 
cyanide baths, etc., with a slight distance between the anodes and 
the objects and with a large anode-surface, it will be advantage- 
ous to couple the elements alongside of each other for quantity ; 
however, for baths with greater resistance and with a greater 
distance of the anodes from the objects, and with a smaller anode 
surface, it is best to couple, the elements one after the other for 
electro-motive force or tension. 

The effects of the electric current are thermal, physiological, 
electro-magnetic, inductive, and chemical ; however, for our pur- 
poses, only the last three need be discussed. 

Electro-magnetism. 

If a wire conveying the electric current be brought near a 
magnetic needle, the latter will immediately be deflected from its 
direction, no matter whether the wire conveying the current be 
placed alongside, above, or beneath the magnetic needle. The 
direction which the needle will assume when placed in any par- 
ticular position to the conducting wire may be determined by the 
following rule : Let the current be supposed to pass through a 
watch from the face to the back : the motion of the north pole loill 
be in the direction of the hands. Or, let the observer imagine him- 
self swimming in the direction of the current with his face toioards 
the needle : the north pole of the needle will then be deflected toivards 
his left hand. 

When the needle is subjected to the action of two currents in 
opposite directions, the one above and the other below, they will 
obviously concur in their effects. The same thing happens when 
the wire carrying the current is bent upon itself and the needle 
placed between the two portions ; and since every time the bend- 
ing is repeated a fresh portion of the current is made to act in 



20 ELECTRO-DEPOSITION OF METALS. 

the same manner upon the needle, it is easy to see how a current, 
too feeble to produce any effect when a simple straight wire is 
employed, may be made by this contrivance to exhibit a powerful 
action on the magnet. It is on this principle that instruments 
called galvanoscopes, galvanometers, or multipliers are constructed. 
They serve not only to indicate the existence of electrical currents, 
but also to show by the effects upon the needle the direction in 
which they are moving. The delicacy of the instrument has been 
increased by Nobili through the use of a very long coil of wire, and 
by the addition of a second needle. This instrument is known 
as the astatic galvanometer. The two needles are of equal size 
and magnetized as nearly as possible to the same extent ; they 
are then immovably fixed together parallel and with their poles 
opposed, and hung by a long fibre of untwisted silk, with the 
lower needle in the coil and the upper one above it. The advan- 
tage thus gained is twofold : the system is astatio, unaffected, or 
nearly so, by the magnetism of the earth ; and the needles being 
both acted upon in the same manner by the current, are urged 
with much greater force than one alone would be, all the actions 
of every part of the coil being strictly concurrent. A divided 
circle is placed below the upper needle, by which the angular 
motion can be measured, and the whole is inclosed in glass, to 
shield the needles from the agitation of the air. 

The deflection of the magnetic needle by the electric current 
has led to the construction of instruments which allow of the 
intensity of the current being measured by the magnitude of the 
deflection. Such instruments are, for instance, the tangent gal- 
vanometer, the sine galvanometer, etc., but they are almost exclu- 
sively used for scientific measurements, while for the determina- 
tion of the intensity of current for electro-plating purposes other 
instruments are employed, which will be described later on. 
However, the electric current exerts not only a reflecting action 
on magnetic needles, but is also capable of producing a magnetiz- 
ing effect on iron and steel. If a bar of iron be surrounded by 
a coil of wire, covered with silk or cotton for the purpose of in- 
sulation, it becomes magnetic so long as the current is conducted 
through the coil. Such iron bars converted into temporary mag- 
nets by the action of the current are called electro-magnets, and 



MAGNETISM AND ELECTRICITY. 21 

they will be the more highly magnetic the greater the number of 
turns of the coil, and the more iutense is the current passing 
through the turns. 

However, not only the iron bar, around which the current 
circulates, becomes magnetic, but also a conducting wire through 
which passes a strong current. By suspending a circular con- 
ducting wire so that it is free to move around its vertical axis, its 
direction is affected by the magnetism of the earth, and it will 
take up a position so that its plane stands at a right angle to the 
plane of the magnetic meridian ; by now conducting the current 
through a wire having the form of a long helix, a so-called sole- 
noid, the wire will, in a like manner, place itself with the turns 
of the helix at right angles to the plane of the magnetic meridian, 
or, in other words, the axis of the solenoid will lie in the mag- 
netic meridian. 

In the same manner as an electrified conducting wire acts upon 
a magnet, two electrified wires exert an attracting and repelling 
influence on each other, the general law of the action being that, 
electric currents moving in parallel lines attract one another, if they 
move in the same direction, and repel one another if they move in 
opposite directions. 

Induction. 

By induction is understood the production of an eleatric cur- 
rent in a closed circuit which is in the immediate neighborhood 
of a current-carrying wire. 

Suppose we have two insulated copper wire spirals, A and B 
(Fig. 5), B being of smaller diameter and inserted in A. When 
the two ends of B are connected with the poles of a battery a 
current is formed in A the moment the current of B is closed. 
This current is recorded by the deflection of the magnetic needle 
of a multiplier, M, which is connected with the ends of A, the 
deflection of the needle showing that the current produced in A 
by the current in B moves in an opposite direction. The current 
in A, however, is not lasting, because, afer a few oscillations, the 
magnetic needle of the multiplier returns to its previous position 
and remains there no matter how long the current may pass 



22 



ELECTRO-DEPOSITION OF METALS. 



through B. If, however, the current in B be interrupted, the 
magnetic needle swings to the opposite direction, thus indicating 
the formation of a current in A, which passes through it in the 
same direction as the interrupted current in B. 



Fis. 5. 




The current causing this phenomenon is called the primary or 
inductive current, and that produced by it in the closed circuit the 
secondary or induced current. From what has been above said, 
it is clear that an electric current at the moment of its formation 
induces in a neighboring closed circuit a current of opposite direc- 
tion, but when interrupted, a current of the same direction. 

In the same manner as closing and opening the inductive 
current, its sudden augmentation also effects the induction of a 
current of opposite direction in a neighboring wire, while its 
sudden weakening induces a current of the same direction ; the 
same effect being also produced by bringing the inductive wire 
closer to, or removing it further from, the neighboring wire. The 
induced currents being alternately formed by opening and closing 
the circuit, and they showing different directions, the term alter- 
nating currents has been applied to them. 

If the turns of the spirals are very close together, each turn 
induces the other, the so-called extra currents being thereby formed. 

The induced currents follow Ohm's law the same as the indue- 



MAGNETISM AND ELECTRICITY. 23 

tive current. A long inducing wire with a small cross-section 
offers greater resistance than a short wire with a larger cross-sec- 
tion, and consequently in the first case the current will possess 
slighter intensity and higher tension, and in the other greater 
intensity and less tension. 

In the same manner as an electrified wire induces a current in 
a neighboring wire, a magnet or electro-magnet also produces in- 
duced currents in a coil of wire surrounding it. These currents 
act in the same manner as those produced by other means, and 
by taking into consideration Ohm's law, currents of great and 
slight intensity can be produced at will, as will be seen in speak- 
ing of the dynamo-electric machines, the construction of which is 
based upon the principle of induction. 

Chemical actions of the electrical current — Electrolysis. 

An electric current on being conducted through a fluid effects 
the reduction of its constituents. By cutting, for instance, the 
conductor of an electric current, and introducing the two wire 
ends thereby formed into water acidulated with dilute sulphuric 
acid, the water, provided the current is strong enough, is decom- 
posed into its constituents, hydrogen and oxygen, the former 
separating in the form of gas on the negative pole and the latter 
on the positive. If such a decomposition does not take place, 
the fluid does not conduct the current. Pure water by itself is a 
bad conductor, and to make its decomposition possible it has to 
be made conductive by acidulation with dilute sulphuric acid. 
When a chemical composition is decomposed by the current, the 
constituent forming the basis of the combination separates on the 
negative pole, and that constituting the acid on the positive ; 
hence metals and hydrogen are liberated on the negative, and 
acids and oxygen on the positive pole. To Faraday is due the 
discovery of the chemical actions of the current and the exposi- 
tion of the laws governing the separation of the constituents. 
He adopted the term electrolysis for the electrical separation of 
chemical combinations, and electrolyte for the fluids subjected to 
electrical decomposition. To the poles or plates leading the cur- 
rent into and out of the electrolyte he applied the term electrodes, 



24 ELECTRO-DEPOSITION OF METALS. 

the positive pole being the anode, and the negative pole the 
cathode. The elements of the electrolyzed liquid, which are 
liberated by the action of the current, are termed ions, those set 
free on the anode or positive electrode being termed anions, and 
those at the cathode or negative anode cations. Thus, when 
acidulated water is electrolyzed, two ions are evolved, namely, 
oxygen and hydrogen, the former at the positive and the latter 
at the negative electrode. 

It is absolutely necessary for the electrolyte to be in a fluid 
state, though it does not matter whether the fluid state is pro- 
duced by solution or fusion. 

We know no more of the actual cause of the chemical action 
of electricity than of its nature and origin. According to 
Clausius's theory, matter is composed of minute particles called 
molecules, which, though mechanically indivisible, are chemically 
divisible ; the constituent parts of the molecules which are no 
further chemically divisible are called atoms. Clausius supposes 
that the molecules are in constant motion ; that in solid bodies they 
move around determined positions of equilibrium, while in fluids 
even apparently tranquil they move from one place to another, 
constantly revolving and pushing against one another without 
being subjected to a return to their original positions. In pushing 
against one another the molecules are decomposed into the atoms 
of which they are composed ; those atoms, however, which have 
become electro-negative under the influence of the current en- 
deavor to reach the anode, while those which have become electro- 
positive move towards the cathode. But in doing this they meet 
atoms of opposite polarity with which they reunite to a molecule 
until they are again liberated by this molecule pushing against 
another, when they move further towards the anode. Arriving 
at the electrodes, they find no more atoms of opposite polarity 
with which they might unite to a molecule ; both atoms, there- 
fore, remain free on the electrodes, while the electrolyte between 
the two electrodes suffers no perceptible change. The atoms are, 
therefore, to be considered as ions. However, in order that the 
ions may be attracted by the electrodes, a current of determined 
electro-motive force is required ; as otherwise, though the electro- 
lyte may conduct the current, the atoms attract one another more 



MAGNETISM AND ELECTEICITY. 



25 



vigorously than they are attracted by the electrode and again form 
molecules. To this mutual attraction of the atoms of opposite 
polarity is due the resistance of the electrolyte to the transmission 
of the current, and also the formation of a current of an opposite 
direction to that of the primary current, which is called the 
counter or polarizing current. This counter current, which is so 
effectually utilized with accumulators (secondary batteries), is the 
worst enemy of the electro-plater, and to overcome it very strong 
currents have frequently to be used, as will be shown, for instance, 
in nickeling sheet zinc. 

Faraday is also the discoverer of the following electrolytic laivs : 
First law. The quantity of substance separated within a deter- 
mined time by the current is directly proportional to the strength of 
the current. By conducting the current through a voltameter 
(Fig. 6), i. e., a closed decomposing cell provided with two plati- 
num electrodes, which are in contact with the poles of the element, 
and dip into acidulated water, oxy- 
gen evolves on the positive electrode 
and hydrogen on the negative. The 
gas mixture (oxy hydrogen gas) is 
conducted through a bent tube in- 
serted air-tight in the stopper of the 
cell, into graduated tubes, in such a 
manner that the gas enters the tubes 
underwater; the escaping mixture of 
gas rises in the form of bubbles into 
the upper part of the tube, and the 
volume of gas there collected in a 
determined time can be readily read 
off. 

Now, if a current of determined 
strength has produced a determined 
quantity of oxyhydrogen gas in the 
voltameter, a current twice as strong" 

will, according to Faraday's law, produce in the same time double 
the volume of gas, from which further results the fact that for 
the decomposition of a determined quantity of any body, a con- 




26 ELECTRO-DEPOSITION OF METALS. 

stant quantity of current is always required, to which the term 
electrical equivalent might be applied. 

Second law. If the same current acts upon a series of different 
solutions, the weights of the elements separated at the same time in 
each solution are proportional to their chemical equivalents. If, 
for instance, the same current be conducted through three decom- 
posing cells, one of which contains water, the second a solution of 
blue vitriol, and the third a solution of nitrate of silver, for each 
gramme of hydrogen developed in the first cell, 31.75 grammes 
of copper will be separated in the second cell, and 108 grammes 
of silver in the third cell, because their chemical equivalents are 
as 1 : 31.75: 108. 

Third law. In an element, the chemical decomposition — the dissolu- 
tion of zinc — is proportional to the strength of current ; or, in other 
words, as many equivalents of zinc are dissolved in the element as 
equivalents of another metal are separated in an inserted electrolyte. 
Every electro-plater observes that the zinc cylinders of the ele- 
ments are dissolved ; and it is just this solution which maintains 
the development of the electric current. As is well known, zinc 
is strongly attacked and dissolved by dilute sulphuric acid ; there- 
fore a dissolution of zinc takes place before the galvanic apparatus 
is closed. This dissolution of zinc, independent of the production of 
current, is termed local action, and to decrease it the zinc is amal- 
gamated by first washing it with strong soda to remove grease. 
Then it is dipped into a vessel of water containing ^-g-th of sul- 
phuric acid; as soon as strong action takes place it is transferred 
to a suitable dish, mercury poured over it, and finally is rubbed 
till a bright silver-like film forms ; then it is set up on edge to 
drain, and before use any globules set free are rubbed off. If 
local action has thus been prevented, only as much zinc will dis- 
solve, according to this law, as is chemically equivalent to the 
metal separated in the decomposing cell. If, however, local action 
is present, the consumption of zinc is increased by the quantity 
corresponding to solution by local action. 

Electro-chemical equivalents. — This term is applied to the 
weights of the various electrolytes which are decomposed in the 
unit of time by the electric unit. The electro-chemical equiva- 
lents are proportional to their chemical equivalents. The electro- 



MAGNETISM AND ELECTRICITY. 27 

chemical equivalent of a body is found by multiplying its chemi- 
cal equivalent by the electro-chemical equivalent of hydrogen 
= 0.0001022. 

When an electric current passes through a conductor, the latter 
becomes more or less heated. According to Joule's experiments, 
it was found that the development of heat in the conductor is. pro- 
portional to its resistance ; and further, that it is proportional to the 
square of the strength of current. 

Hence the development of heat will be the greater the smaller 
the cross-section of the conductor and its conducting capacity are ; 
and the larger the quantity of current which passes through it. 
For practical purposes, the conclusion derived from this is the 
necessity of choosing conducting wire of good conducting capacity 
and of sufficiently large diameter to prevent the development of 
heat, which in this case means loss of current. 

Consumption of power in electrolysis. — Without a desire fur- 
ther to enter into the details of the electro-chemical theory, it 
may, for the sake of completeness, be mentioned that the force re- 
quired for the decomposition of an electrolytic solution is at least 
equal to that which, when converted into heat, corresponds to the heat 
developed by the separated bodies in their reunion into their original 
combination. 

Electric units. — The electro-motive force required for the de- 
composition being frequently given, as well as the intensity which 
the current must possess in order properly to coat a determined 
surface of articles with the elect rolytically separated metal, the 
electric units serving for electric measures will be briefly given : — 

To measure the physical phenomena of the current it is neces- 
sary to refer to mass, length, and duration of time, and the units 
adopted by the International Congress of 1881 are as follows : — 

1. Unit of length, 1 centimetre. 

2. Unit of time, 1 second. 

3. Unit of mass, the mass of one gramme. 

The term fundamental or C. G. S. (centimetre-gramme-second) 
units lias been applied to this system. 

Force or power (F) — Dyne. — Force which acting upon 1 
gramme for a second generates a velocity of 1 centimetre per 
second. 



28 ELECTRO-DEPOSITION OF METALS. 

Work — Erg. — Amount of work done by 1 dyne working 
through 1 centimetre of distance. 

Quantity. — The quantity conveyed by unit current in 1 second. 

Potential or electromotive force. — The difference of the electric 
condition between two conductors or two points of a conductor, 
when the transference of electricity from one to the other is pro- 
ceeding at the rate of 1 erg of work per unit of electricity trans- 
ferred. 

Resistance. — A resistance such that with unit of difference of 
potential between the ends of conductor, 1 unit of current is con- 
veyed along it. 

Of the so-called practical units, which were retained by the 
Congresses and Conferences of 1881 and 1884, there are five : the 
ohm, volt, ampere, farad , and coulomb. 

The ohm is the practical unit of resistance. It is equal to the 
resistance of a column of mercury 1 metre long and 1 square mil- 
limetre in cross-sectional area at 0° C, and approximately equal 
to the resistance of 48.5 metres of pure copper wire, 1 millimetre 
in diameter, at 0° C. The ohm is equal to 10 9 C. G. S. units. 

The ampere is the practical unit of the current-strength (inten- 
sity) ; it is equal to j- 1 ^- of the theoretical C. G. S. unit. For 
practical purposes the quantity of silver precipitated in one second 
is taken as the representative value of an ampere, 0.0011188 
gramme of silver corresponding, according to Kohlrausch, to one 
ampere. 

The volt is the practical unit of the electro-motive force, and is 
equal to 10 8 C. G. S. units. It is approximately equal to the 
electro-motive force of a single Daniell's cell. 

The farad is the practical unit of capacity equal to 10 9 C. G. S. 
units ; the coulomb is the unit of quantity, i. e., the volume of 
current equal to that of 1 ampere passing through a circuit for 
one second of time. 

A current of 1 ampere at the pressure of 1 volt is termed a 
watt ; it is a most useful unit for comparing different currents, 
and is really the product of volume into pressure. 

The English horse-power (H. P.) is taken at 550 foot-pounds 
per second, and is thus equivalent to raising 550 pounds through 
one foot; or, one pound through 550 feet in a second. (The 
French H. P. is 542.48 foot-pounds per second.) 



GALVANIC ELEMENTS, THERMOPILES, ETC. 29 



III. 

SOURCES OF CURRENT. 



CHAPTER III. 

GALVANIC ELEMENTS — THERMO-PILES — MAGNETO- AND 
DYNAMO-ELECTRIC MACHINES. 

The sources of current used for electro-deposition of metals 
are the galvanic elements, thermo-piles, magneto-electric machines, 
and dynamo-electric machines. 

A. Galvanic Elements. 

It is not proposed to enter into a detailed description of all the 
forms of galvanic elements, because the number of such construc- 
tions is very large, while the number of those which have been 
successfully and permanently introduced for practical work is 
comparatively small. 

The original form of the galvanic elements, the voltaic pile, 
consisting of zinc and copper plates separated from one another 
by moist pieces of cloth, has been already mentioned on p. 2, as 
well as its disadvantages which led to the construction of the so- 
called trough battery. The separate elements of this battery are 
square plates of copper and zinc, soldered together and parallel, 
fixed into water-tight grooves in the sides of a wooden trough so 
as to constitute water-tight partitions which are filled with acidu- 
lated water. The layer of water serves here as a substitute for 
the moist pieces of cloth in the voltaic pile. 

In other constructions the fluid is in different vessels, each 
vessel containing a zinc and a copper plate which do not touch 
one another in the same vessel, the copper plate of the one vessel 
being connected with the zinc plate of the next, and so on. 



30 ELECTRO-DEPOSITION OF METALS. 

In all elements with one fluid as an excitant, the current is 
quite strong at first, but quickly decreases for the following rea- 
sons : First, during the interruption of the current a change takes 
place in the fluid by the local action in the element, and then 
with a closed circuit the zinc with the impurities it contains forms 
small voltaic piles, the element consequently also performing a 
certain chemical work during the interruption of the current. As 
mentioned on p. 26, the local action can be reduced to a minimum 
by amalgamating the zinc. Such amalgamation is also a protec- 
tion against the above-mentioned chemical work of the element, 
the bubbles of hydrogen adhering so firmly to the amalgamated 
homogeneous surface as to form a layer of gas around the zinc 
surface, which prevents its contact with the fluid. 

Amalgamation may be effected in various ways. The zinc is 
either scoured with coarse sand moistened with dilute sulphuric 
or hydrochloric acid, or pickled in a vessel containing either of 
the dilute acids. The mercury may be either mixed with moist 
sand and a few drops of dilute sulphuric acid, and the zinc be 
amalgamated by applying the mixture by means of a wisp of 
straw or a piece of cloth ; or the mercury may be applied by itself 
by means of a steel wire brush, the brush being dipped in the 
mercury, and what adheres quickly divided upon the zinc by 
brushing until the entire surface acquires a mirror-like appear- 
ance. The most convenient mode of amalgamation is to dip the 
zinc in a suitable solution of a mercury salt and rub with a woollen 
rag. A suitable solution is prepared by dissolving 10 parts by 
weight of mercurous nitrate in 100 parts of warm water, to which 
pure nitric acid is added until the milky turbidity disappears. 
Another solution, which is also highly recommended, is obtained 
by dissolving 10 parts by weight of mercuric chloride (corrosive 
sublimate) in 12 parts of hydrochloric acid and 100 of water. In 
order to preserve as much as possible the coating of mercury upon 
the zinc, sulphuric acid saturated with neutral mercuric sulphate 
is used for the elements; for which purpose frequently shake the 
concentrated sulphuric acid (before diluting with water) with the 
mercury salt. 

Bouant recommends instead of the addition of mercuric sul- 
phate, to compound the dilute sulphuric acid with 2 per cent, of 



GALVANIC ELEMENTS, THERMOPILES, ETC. 31 

a solution obtained as follows : Boil a solution of 3| ozs. of nitrate 
of mercury in 1 quart of water, with an excess of a mixture of 
equal parts of mercuric sulphate and mercuric chloride, and, after 
cooling, filter and use the clear solution. 

The third reason for the decrease of the current-strength in 
elements with one fluid is polarization. By polarization is under- 
stood the appearance in the element of a second current which, 
being opposite to that produced by the element, weakens the action 
of the latter. The cause of galvanic polarization is found in the 
fact that the negative pole-plate becomes coated with a layer of 
hydrogen, whereby according to Clausius's theory (p. 24) the 
attraction of the anodes for the ions is essentially weakened, while, 
according to another theory, the eleetro-negative plate, by contact 
with the layer of gas, becomes electro-positive towards the other, 
which is coated with bubbles of oxygen. 

Polarization can only be entirely avoided in elements the nega- 
tive pole-plate of which dips into a fluid which oxidizes the 
hydrogen to water, as is the case in the so-called constant elements 
with two fluids, as will be seen later on. 

Proceeding from the conviction that rough surfaces allow the 
bubbles of hydrogen to pass off much more freely than smooth 
surfaces, Smee constructed the element named after him. It 
consists of a zinc plate and a platinized silver plate dipping into 
dilute acid. It may be formed of two zinc plates mounted with 
the platinized silver between them in a wooden frame, which being 
a very feeble conductor may carry away a minute fraction of the 
current, but serves to hold the metals in position, so that quite a 
thin sheet of silver may be employed without fear of its bending 
out of shape and making a short circuit. The platinizing is 
effected by hanging the silver plates in a vessel filled with acidu- 
lated water, adding some chloride of platinum and placing the 
vessel in a porous clay cell filled with acidulated water and con- 
taining a piece of zinc, the latter being connected with the silver 
plates by copper wire. The platinizing obtained in this manner 
is a black powder which roughens the surfaces, in consequence of 
which the bubbles of hydrogen become readily detached and the 
polarization is less than with silver plates not platinized. The 
use of electrolytically prepared copper plates, which are first 



32 



ELECTRO-DEPOSITION OF METALS. 



Fig. 7. 



strongly silvered and then platinized, is still more advantageous 
on account of their greater roughness. To increase the constancy 
of the element, it is advisable to add some chloride of platinum 
to the dilute acid of the element. The electro-motive force of the 
Smee element is about 0.48 volt. 

As previously mentioned, polarization can be entirely avoided 
only by allowing the electro-negative pole plate to dip in a fluid 
which, by combustion, reduces the hydrogen evolved to water, 
or, in other words, which immediately oxidizes the hydrogen to 
water. From this conviction originated the so-called constant 
elements with two fluids, the first of these elements being, in 1829, 
constructed by Becquerel, which, in 1836, was succeeded by the 
far more effective one of Daniell. 

As most generally used, Daniell's element (Fig. 7) consists of a 
glass vessel, a copper cylinder, a porous clay cell, and a rod of 
zinc suspended in the latter. The glass ves- 
sel is filled with concentrated solution and 
a small piece of blue vitriol, and the porous 
clay cell with dilute sulphuric acid. The 
oxygen evolved on the electro-positive zinc 
oxidizes the latter, sulphate of zinc being 
formed, while the hydrogen separating on 
the electro-negative copper reduces from the 
blue vitriol solution a quantity of copper 
equivalent to it, which separates upon the 
electro-negative plate. However, after a 
comparatively short time of working, the 
dilute sulphuric acid is consumed for the formation of sul- 
phate of zinc, the electro-motive force becoming very weak ; the 
necessity of frequently renewing the dilute sulphuric acid is an 
inconvenience which the Daniell elements show more than any 
others. Furthermore, by the action of osmose blue vitriol solu- 
tion gets into the porous cell, where it is decomposed by coming 
in contact with the zinc, the copper being separated upon the 
latter, whereby the eifect is destroyed or at least very much 
weakened. The electro-motive force of the Daniell element is 
about 1 volt. 




GALVANIC ELEMENTS, THERMOPILES, ETC. 



33 



'icr. 



The Meidinger element may be considered a modified Daniell 
element. Like the Callaud element, it has no porous division, 
the mixture of the two fluids being prevented by their different 
specific gravities. The shape of the Meidinger element, as most 
generally used, is shown in Fig. 8. 

Upon the bottom of a glass vessel, A, provided at b with a 
shoulder, stands a small glass cylinder, ft, which contains the 
electro-negative copper cylinder D; from 
the latter a conducting wire leads to the 
exterior. Upon the shoulder, at b, rests the 
zinc cylinder Z, which is also provided with 
a conducting wire leading to the exterior. 
The balloon C closes the vessel by being 
placed upon it. The balloon is filled with 
pieces of blue vitriol and Epsom salt solu- 
tion ; the entire element is also filled with 
Epsom salt solution (1 part Epsom salt to 
5 water). In the balloon C concentrated 
solution of blue vitriol is formed which 
flows into the glass cylinder K ; if the cir- 
cuit is not closed, the concentrated copper 
solution remains quietly standing in K, its 
greater specific gravity preventing it from 

rising higher and reaching the zinc. If, however, the circuit be 
closed, zinc is dissolved, while metallic copper is separated from 
the blue vitriol solution, and concentrated solution flows from the 
balloon Cto the same extent as the blue vitriol solution in D 
becomes dilute by the separation of copper. Hence the action of 
the element remains constant for quite a long time, and of all 
the modified forms of Daniell's element consumes the least blue 
vitriol for a determined quantity of current ; however, in conse- 
quence of its great internal resistance (9.90 ohms) its current- 
strength is small. The electro-motive force of the Meidinger 
element is 0.95 volt. 

Grove, in 1839, substituted platinum for copper; the platinum 

dips in concentrated nitric acid, while the zinc cylinder stands in 

dilute sulphuric acid. The hydrogen liberated on the platinum 

is oxidized to water by the nitric acid, hyponitrous acid escaping 

3 




34 ELECTRO-DEPOSITION OF METALS. 

in the form of gas. The electro-motive force of the Grove ele- 
ment is at first double that of the Daniell element, but it soon 
abates on account of the dilution of the nitric acid by water. 
To prevent this weakening, concentrated sulphuric acid, which 
absorbs the water formed by the oxidation of the hydrogen, may 
be added to the nitric acid. Though the resistance of the Grove 
element is small (0.70 to 0.75 ohm), and its electro-motive force 
1.70 to 1.90 volts, according to the concentration of the solutions, 
it is but seldom used on account of its costliness. 

Bunsen, in 1841, replaced the expensive platinum by prisms 
cut from gas-carbon, which is still less electro-negative than 
platinum, and very hard and solid, so that it perfectly resists the 
action of the nitric acid. In place of the gas-carbon an artificial 
carbon may be prepared by kneading a mixture of pulverized 
coal and coke with sugar solution or syrup, bringing the mass 
under pressure into suitable iron moulds and glowing it with the 
exclusion of air. After cooling, the carbon is again saturated 
with sugar solution (others use tar, or a mixture of tar and glycer- 
ine) and again glowed with the exclusion of air, these operations 
being, if necessary, repeated once more, especially when great 
demands are made on the electro-motive force and solidity of the 
artificial carbons. 

Figs. 9, 10, and 11 show the three forms of Bunsen's elements 
most generally used. 

Fig. 9, which is the most convenient and practical form, con- 
sists of an outer vessel of glass. In this is placed a cylinder of 
zinc in which stands a porous clay cell, and in the latter the 
prism of gas-carbon. A band of copper is soldered or secured 
by means of a binding-screw to the zinc cylinder, while the prism 
of gas-carbon carries the binding-screw (armature), as seen in 
Fig. 8, in the upper part of which a copper sheet or wire is fixed 
for the transmission of the current. The outer vessel is filled 
with dilute sulphuric acid (1 part by weight of sulphuric acid of 
66° Be. — free from arsenic — and 15 parts by weight of water), 
and the porous cell with concentrated nitric acid of at least 36° 
Be., or still better 40° Be., care being had that both fluids have 
the same level. 

In Fig. 10 the cylinder of artificial carbon is in the glass 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



35 



vessel, while the zinc, which, in order to increase its surface, has a 
star-like cross-section, is placed in the porous clay cell. In this 
case the outer vessel is filled with concentrated nitric acid, and 
the clay cell with dilute sulphuric acid. 



Fie. 9. 




Fig. 10 



Fig. 11. 





The form of the Bunsen element shown in Fig. 9 is more 
advantageous, because its effective zinc surface can be kept larger. 
Fig. 11 shows a plate element such as is chiefly used for bichro- 
mate batteries. 



Fie. 12. 




Improved Bunsen cell. — Fig. 12 shows an improved type of 
Bunsen cell for nickel-plating purposes, where the absence of 
power prevents the use of a dynamo machine. This cell fur- 



;g 



ELECTRO-DEPOSITION OF METALS. 



nishes a large volume of current, as its internal resistance is low. 
It is an easy battery to set up and keep in working order. The 
batteries are set up by well amalgamating, inside and out, the 
zinc 2, Fig. 13, and placing it in the jar 1. Inside the zinc 




place the porous cup 3, and within the porous cup the carbon 4, 
and then pour nitric acid in the porous cup. In the outer jar 
pour a mixture of 1 part sulphuric acid to 12 of water (previ- 
ously mixed and allowed to cool). This acid mixture should 
cover the zinc or be on a level with the liquid in the porous cup. 
When the liquid in the outer jar becomes milky, withdraw it 
with a syringe or siphon, and refill, adding occasionally small 
quantities of nitric acid to the porous cup, and keeping the zinc 
thoroughly amalgamated by one of the methods given on page 
30. A very good plan of amalgamating zinc is as follows : Dip 
in lye to remove grease, rinse, then dip in the dilute acid in the 
glass jar, and then brush over with about 2 ozs. of mercury con- 
tained in a little flannel bag. 

JEledropoion may be substituted for the nitric acid in the porous 
cup. This battery liquid consists of 1 lb. of bichromate of pot- 
ash dissolved in 10 lbs. of water, to which 2 J lbs. of commercial 
sulphuric acid have been gradually added. 

The Bunsen elements are much used for electro-deposition, since 
they possess a high electro-motive force (1.88 volts) and, on 
account of slight resistance (0.25 ohm), develop considerable cur- 
rent-strength. Like the Grove elements, they have the incon- 
venience of evolving vapors of hyponitrous acid, which are not 



GALVANIC ELEMENTS, THERMOPILES, ETC. 37 

only injurious to health, but also attack the metallic articles in 
the workshop. Wherever possible they should be placed in a box 
at such a height that they may be readily manipulated. This 
box should have means of ventilation in such a way that the air 
coming in at the lower part will escape at the top through a flue, 
and carry away with it the acid fumes disengaged. It is still 
better to keep the elements in a room separate from that where 
the baths and metals are to be operated upon. Furthermore, as 
the nitric acid becomes diluted by the oxidation of the hydrogen, 
and the sulphuric acid is consumed in the formation of sulphate 
of zinc, the acids have to be frequently renewed. 

To avoid the acid vapors, as well as to render the elements 
more constant, A. Dupre has proposed the use of a 30 per cent, 
solution of bisulphate of potash in water in place of the dilute 
sulphuric acid, and a mixture of water 600 parts, concentrated 
sulphuric acid 400, sodium nitrate 500, and bichromate of potash 
60, in place of the nitric acid. 

The following method can be recommended : The outer vessel 
which contains the zinc cylinder is filled with a moderately con- 
centrated (about 30 per cent.) solution of bisulphate of potash or 
soda, and the clay cell with solution of chromic acid — 1 part 
chromic acid to 5 parts water. As soon as the electro-motive 
force of the element abates, it is strengthened by the addition of 
a few spoonfuls of pulverized chromic acid to the chromic acid 
solution. It is better to use the chromic acid in the form of 
powder, which is especially prepared for this purpose, than a 
chromic acid solution produced by mixing solution of bichromate 
of potash with sulphuric acid, the tendency of such a solution to 
form crystals exerting a disturbing effect. 

In using nitric acid it is also advantageous to pour a 0.39 to 
0.78 inch thick layer of oil upon the acid to decrease the vapors. 

The binding-screws which effect the metallic contacts must of 
course be frequently inspected and cleaned, which is best done by 
means of a file or emery paper. It is advisable to place a piece 
of sheet platinum between the binding surface of the carbon 
armature and the carbon in order to prevent the acid rising through 
the capillarity of the carbon from acting directly upon the arma- 
ture (generally brass or copper). To prevent the acid from 



38 ELECTRO-DEPOSITION OF METALS. 

rising, the upper portions of the carbons may be impregnated with 
paraffine. For this purpose the carbons are placed f to 1 inch 
deep in melted paraffine and allowed to remain 10 minutes. On 
the sides where the armature comes in contact with the carbon, 
an excess of paraffine is removed by scraping with a knife-blade 
or rasp. 

Manipulation of JBunsen elements. — Before using the elements 
the zinc cylinders should be very carefully amalgamated according 
to one of the methods given on p. 30. The nitric acid need not 
be pure, the crude commercial acid suffices, but it should be as con- 
centrated as possible and show at least 36° Be. For the prisms 
it is best to take carbon produced in gas-houses using coal without 
the addition of brown coal, the electro-motive force of the latter 
being less. If artificial carbon is employed, it should be ex- 
amined as to its suitability, the non-success of the plating process 
being frequently attributed to the composition of the bath, when in 
fact it is due to the defective carbons of the elements. In order to 
avoid an unnecessary consumption of zinc and acid the elements 
are taken apart when not in use, for instance, over night. Detach 
the brass armature of the carbon prism and lay it in water to 
which some chalk has been added ; lift the carbon from the clay 
cylinder and place it in a porcelain dish or earthenware pot ; 
empty the nitric acid of the clay cell into a bottle provided with 
a glass stopper ; place the clay cell in a vessel of water, and finally 
take the zinc cylinder from the dilute sulphuric acid and place it 
upon two sticks of wood laid across the glass vessel to drain off. 
In putting the elements together the reverse order is followed, 
the zinc being first placed in the glass vessel and then the carbon 
in the porous clay cell. The latter is then filled about three- 
quarters full with used nitric acid, and fresh acid is added until 
the fluid in the clay vessel stands at a level with that in the outer 
vessel. The cleansed brass armature is then screwed upon the 
carbon prism. Finally, add to the dilute sulphuric acid in the 
outer vessel a small quantity of concentrated sulphuric acid 
saturated with mercury salt. 

It is advisable to have at least a duplicate set of porous clay 
cells, and in putting the elements together to use only cells which 
have been thoroughly soaked in water. The reason for this is as 



GALVANIC ELEMENTS, THERMOPILES, ETC. 39 

follows : The nitric acid fills the pores of the cell, and, finally 
reaching the zinc of the outer vessel, causes strong local action and 
a correspondingly rapid destruction of the zinc. It is, therefore, 
best to change the clay cells every day, allowing those which have 
been in use to lie in water the next day with frequent renewal of 
the water. For the same reason the nitric acid in the clay cell 
should not be at a higher level than the sulphuric acid in the 
outer vessel. 

When the Bunsen elements are in steady use from morning till 
night, the acids will have to be entirely renewed every third or 
fourth day. The solution of sulphate of zinc in the outer vessel 
is thrown away, while the acid of the clay cells may be mixed 
with an equal volume of concentrated sulphuric acid, and this 
mixture can be used as a preliminary pickle for brass and other 
copper alloys. 

The Leclanehe element (zinc and carbon in sal ammoniac solu- 
tion with manganese peroxide as a depolarizator) need not be 
further mentioned, it not being adapted for regular use in electro- 
plating. It is in very general use for electric bells, its great 
recommendation being that, when once charged, it retains its power 
without attention for several years. 

Lallande and Chaperon have recently introduced a copper oxide 
element, shown in Fig. 14, which possesses several advantages. 
It consists of the outer vessel G, of cast-iron or copper, which 
forms the negative pole surface, and to which the wire leading to 
the anodes is attached, and a strip of zinc, Z, coiled in the form 
of a spiral, which is suspended from an ebonite cover carrying a 
terminal connected with the zinc. The hermetical closing of the 
vessel G by the ebonite cover is effected by means of three screws 
and an intermediate rubber plate. Upon the bottom of the ves- 
sel G is placed a 3 to 4 inch deep layer of copper oxide, 0, and 
the vessel is filled with a solution of 50 parts of caustic potash 
in 100 of water. When the circuit is closed, decomposition of 
water takes place, the oxygen which appears on the zinc forming 
with the latter zinc oxide, which readily dissolves in the caustic 
potash solution, while the hydrogen is oxidized with the simul- 
taneous reduction of copper oxide to copper. When the element 
is open, i. e., the circuit not closed, neither the zinc nor the copper 



40 



ELECTRO-DEPOSITION OF METALS. 



oxide is attacked, and hence no local action nor any consumption 
of material takes place. The electro-motive force of this element 
is 0.98 volt, and its internal resistance very low. It is remarka- 
bly constant and is well adapted for electro-plating purposes by 



Fiar. 14, 




using; two of them for one Bunsen element. The following; rules 
have to be observed in its use. It is absolutely necessary that 
the ebonite cover should hermetically close the vessel G, as other- 
wise the caustic potash solution would absorb carbonic acid from 
the air, whereby carbonate of potash would be formed, which 
would weaken the exciting action of the solution. Further, the 
vessel G forming the one pole must be insulated from the other 
as well as from the ground, as otherwise a loss of current or de- 
fective working would be the consequence. 

The elements of Marie Davy, Niaudet, Duchemin, Sturgeon, 
Trouville, and others, being of little value for practical use, may 
be passed over. 

Duns's potash element. — On account of its great electro-motive 
force (1.6 volts) and slight internal resistance this element would 
be well adapted for electro-plating purposes, if depolarization 
were effected more rapidly than is actually the case. Its construc- 
tion is as follows : In a glass vessel stands a carbon cylinder 



GALVANIC ELEMENTS, THEKMO-PILES, ETC. 41 

closed below, and in the centre of the carbon cylinder a clay cell. 
The space between the clay cell and the interior wall of the 
carbon cylinder is filled five-sixths full with pieces of carbon. In 
the clay cell stands an amalgamated strip of zinc or zinc cylinder 
to which the conducting wires are soldered, the place of soldering, 
as well as the wire as far as it comes in contact with the fluid, 
being covered with gutta-percha. The edge of the carbon cylinder 
is coated with paraffine and carries the pole binding-screw. The 
filling of the element is effected by laying potassium permanga- 
nate in crystals upon the layer of carbon between the clay and 
carbon cylinders, and pouring a solution of 1 part of pure caustic 
potash in 2 of water into the clay cell, the pouring being continued 
until the fluid runs over the clay cell upon the potassium perman- 
ganate and the layer of carbon, and finally fills the outer vessel 
up to about the breadth of two fingers from the edge. The 
action of the element is as follows : When the element is closed 
decomposition of water takes place, the oxygen combining with the 
zinc to form zinc oxide, which is dissolved by the potash lye, while 
the hydrogen is oxidized on the positive pole by the potassium 
permanganate. The latter, to be sure, contains much oxygen, and 
acts very energetically, but as it diffuses very slowly, depolariza- 
tion, i. e., the removal of the hydrogen, is not so quickly effected 
as, for instance, in the Bunsen element, where the nitric acid 
rapidly diffuses. Hence with a slight external resistance, for 
instance, baths where the element has to furnish large quantities 
of current, the electro-motive force sinks very rapidly and with it 
the current-strength, and, therefore, the element is only suitable for 
electro-plating purposes when a current need only for a short time 
be produced, but not for permanent work. In the first case it offers 
the advantage of being always ready for use, evolving no vapors, 
and when not in use consuming no material. It is prudent to 
protect this element from the action of the carbonic acid of the 
air by a close cover. 

The element shown in Fig. 15 has recently been patented in 
Germany, and is described by Knaffe and Kiefer,* of Vienna, as 
follows : The element consists of a combination of zinc and car- 

* Neueste Erfindungen und Erfahrurigen, vol. xviii. p. 308. 



42 



ELECTRO-DEPOSITION OF METALS. 



Fig. 15. 



bon. The zinc plate is 9 J inches long, 4f inches wide, and of the 
thickness of pasteboard. It is amalgamated according to a new 
process. It is placed between two carbon 
plates of equal size, the surface of which 
is twice that of the zinc. The carbon 
plates are connected with the conducting 
wires in such a manner as to prevent 
oxidation of the binding-screws and to 
secure constant contact. The zinc plate 
is suspended in a neutral salt solution in 
a clay cell, the space between the latter 
and the carbon plates being filled with 
pieces of carbon. The consumption of 
zinc is very small. The principal advan- 
tage of this new element is, however, the 
depolarizing fluid of peculiar composition 
and powerful effect. 

The element has an electro-motive force 
of 1.9 volts, an internal resistance of 0.17 
ohm, and a constancy such as has never 
before been attained with primary ele- 
ments, 1 volt ampere lasting for 100 
hours. 

We will add a few words in regard to 
plunge or bichromate batteries. They 
consist of a number of separate voltaic 
cells connected so as to form a single cell 
or electric source, and the plates of which 
are so supported as to be capable of being simultaneously placed 
in or removed from the exciting fluid. For our purposes it will 
suffice to mention the Bunsen plunge battery, shown in Fig. 16. 
For constructive reasons only one fluid is used, into which the 
zinc as well as the carbon plates dip, a solution of chromic acid 
prepared by dissolving 10 parts of bichromate of potash and J 
part of mercuric sulphate in 100 parts of water, and adding 18 
parts of pure concentrated sulphuric acid, being employed. More 
advantageous is a solution of chromic acid in the form of powder 




GALVANIC ELEMENTS, THERMOPILES, ETC. 



43 



in water, in the proportion of 1:5, for the same reason as given 
on p. 37. 



Fig. 16. 




Fig. 17 shows a bichromate battery as constructed by Fein. 
Into the 6 element-vessels standing in two rows in the wooden 
box M dip the zinc and carbon plates, which are secured to 
woodeu cross-pieces provided with handles, and may be main- 
tained at any desired height by the notch e in the standard G. 
According to the current-strength required, the plates are allowed 
to dip in more or less deeply. 

Fig. 1 8 shows a bichromate battery as constructed by Keiser & 
Schmidt. 

In using the above-mentioned chromic acid solution, which 
has been recommended by Bunsen, the elements at first develop 
a very strong current, which, however, in a comparatively short 
time becomes weaker and weaker. The current-strength can be 
increased by adding at intervals a few spoonfuls of pulverized 
chromic acid to the chromic acid solution, which, however, finally 
remains without effect, when the battery has to be freshly filled. 



44 



ELECTRO-DEPOSITION OF METALS. 
Fig. 17. 




Fig. 18. 



Hence, these batteries are not suitable for electro-plating opera- 
tions requiring a constant current for some time. 

For temporary use, for instance, by 
gold-workers and others, for gilding or 
silvering small articles, the bottle-form 
of the bichromate element (Fig. 19) may 
be advantageously employed. In the 
bottle A two long strips of carbon 
united above by a metallic connection 
are fastened parallel to one another to 
a vulcanite stopper, and are there con- 
nected with the binding-screw ; these 
form the negative element, and pass to 
the bottom of the bottle • between them 
is a short thick strip of zinc attached 
to a brass rod passing stiffly through 
the centre of the vulcanite cork, and connected with the binding- 
screw. The zinc is entirely insulated from the carbon by the 




GALVANIC ELEMENTS, THERMOPILES, ETC. 



45 



vulcanite, and may be drawn out of the solution by means of the 
brass rod as soon as its services are no longer required. 

This bichromate element is excellent for purposes requiring 
strong currents, where long action is not necessary. As this ele- 
ment readily polarizes, it cannot be advantageously employed 
continuously for any considerable period of time. It becomes 
depolarized, however, when left for some time on open circuit. 
The element gives an electro-motive force of about 1.9 volts. 

In Stoehrer's battery (Fig. 20) two acids, dilute sulphuric acid 
and concentrated nitric acid, are used. The porous clay cell is 



Fig. 19. 



Fig. 20. 





omitted, the massive carbon cylinders K K, etc., being provided 
with a cavity reaching almost to the bottom, which is filled with 
sand and nitric acid. The contact of the carbon and zinc cylin- 
ders is prevented by glass beads imbedded in the carbon cylinders. 



46 ELECTRO-DEPOSITION OF METALS. 

B. Thermo-electric Piles. 

Though thermo-electric piles are only used in isolated cases for 
electro-plating operations, for the sake of completeness their 
nature and best known forms will be briefly mentioned. 

In the year 1822 Professor Seebeck, of Berlin, discovered a new 
source of electricity, namely, inequality of temperature and con- 
ducting power in different metals, or in the same metal in different 
states of compression and density. When two pieces of different 
metals, connected together at each end, have one of their joints 
more heated than the other, an electric current 
Fig. 21. - g i mm ediately set up. Of all the metals tried, 

bismuth and antimony form the most powerful 
combination. 

In Fig. 21 Bm represents a bar of bismuth, 
and mS a bar of antimony soldered to the 
bismuth bar. By leading wires from B and 8 
to a galvanoscope, G, and heating the point of 
junction m, the needle of the galvanoscope is 
deflected. From this it may concluded that 
an electric current circulates in the closed 
circuit GB mS G. By a closer examination 
the direction of the current may be recognized, 
it flowing on the heated point of junction from the bismuth to the 
antimony, and in the connecting wire of the ends of the rods 
which remain cold, from the antimony to the bismuth. The cur- 
rent is the stronger the greater the difference in the temperature 
of the point of junction and the free ends of the bars. Hence 
the electric current will be especially strong when the place of 
junction is heated and the ends B and S are at the same time 
cooled off. A combination as above described is called a thermo- 
electric couple, and the electricity obtained in this manner thermo- 
electricity. By a suitable combination of several or many of such 
couples, a thermo electric pile is obtained. 

JVbe's thermo-electric pile (Fig. 22) consists of a series of small 
cylinders, composed of an alloy of 36J parts of zinc and 62i 
parts of antimony for the positive element, and stout German 
silver as the negative element. The junctions of the elements are 




GALVANIC ELEMENTS, THERMOPILES, ETC. 



47 



heated by small gas-jets, and the alternate junctions are cooled by 
the heat being conducted away by large blackened sheets of thin 

Fig. 22. 





copper. A pile of twenty pairs has an electro -motive force of 
1.9 volts. 

ClamoncVs thermo-electric pile (Fig. 23) consists of an alloy of 
2 parts antimony and 1 of zinc for the negative metal, while for 

Fig. 23. 




the positive element ordinary tinned sheet-iron is employed, the 
current flowing through the hot junction from the iron to the 



48 



ELECTRO-DEPOSITION OF METALS. 



alloy. To insure a good contact between the two metals a strip 
of tin-plate is bent into a narrow loop at one end. This portion 
is then placed in a mould and the melted alloy poured around it, 
so that it is actually imbedded in the casting. The pile shown in 
the illustration consists of five series, one placed above the other. 
Each series has ten elements grouped in a circle, and is insulated 
from the succeeding series by a layer of cement, composed of 
powdered asbestos moistened with a solution of potassium silicate. 
AVith the consumption of about (ij cubic feet of gas per hour, 
such a pile precipitates 0.7 oz. of copper, which corresponds to an 
electro-motive force of about 17 amperes. 

Hauck's thermo-electric pile. — An essential defect of (Diamond's 
thermo-electric pile consists in that the junctions of the dissimilar 

Fig. 24. 




metals are subjected to ready destruction by being exposed to the 
direct action of the flame. Further, it is very difficult, or at least 
inconvenient, to make repairs, since in such a case it may become 
necessary to take the entire pile apart. Hauck has successfully 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



49 



overcome these defects by adopting the principle of indirect heat- 
ing as well as by giving the couples a more suitable form and by 
improving the alloy. The couples form four-sided wedges to 
which are attached cast-iron pieces that transfer the heat of the 
gas-burner to the couples. The electro-motive force of a single 
couple is y 1 -^ that of a Daniell element. Fig. 24 shows a combina- 
tion of two piles standing upon a common plate, one of the piles 
being given in cross-section. The glass- vessel H, with the tubes B, 
G, R, i, serves as a regulator for the gas-pressure. The pile shown 
in the illustration serves for the production of metallic deposits 
on a small scale, especially for analytical examinations. Hauck, 
however, also furnishes combinations of three larger piles. 

Giilcher's thermo-electric pile, invented in 1890, is shown in 
Fig. 25. It is arranged for gas-heating, and with a constant sup- 
ply of gas requires a pressure-regulator. The negative electrodes 
consist of nickel and the positive electrodes of an antimony alloy, 

Fig. 25. 




the composition of which is kept secret. The negative nickel 
electrodes have the form of thin tubes and are secured in two rows 
in a slate plate, which forms the termination of a gas conduit with 
a U-shaped cross-section beneath it. Corresponding openings in 
the slate plate connect the nickel tubes Avith the gas conduit, the 
latter being connected by means of a rubber tube with the pipe 
supplying the gas. Thus the gas first passes into the conduits, next 
into the nickel tubes, and leaves the latter through six small holes 
in a soap-stone socket screwed in the end of each tube. On 
leaving these sockets the gas is ignited and the small blue flames 
heat the connecting piece of the two electrodes. This connecting 
4 



50 ELECTEO-DEPOSITION OF METALS. 

piece consi8ts of a circular brass plate placed directly over the 
soap-stone socket. One end of it is soldered to the nickel tube, 
while the other ends, towards the top, in a socket in which are 
cast the positive electrodes. The latter have the form of cylin- 
drical rods with lateral angular prolongations. To the ends of 
these prolongations are soldered long copper strips secured in 
notches in the slate plate. They serve partially for cooling off 
and partially for connecting the couples. For the latter purpose 
each copper strip is connected by a short wire with the lower 
end of the nickel tube belonging to the next couple. When the 
pile is to be used, the gas is ignited in one place, the ignition 
spreading rapidly through the entire series of couples. In about 
10 minutes the junctions of the metals have attained their highest 
temperature and the pile its greatest power, which, with a con- 
stant supply of gas, remains unchanged for days or weeks. 

In view of the conversion of the heat produced by the com- 
bustion of the gas into electricity, the useful effect of the thermo- 
electric pile can be considered only a very slight one. One cubic 
meter of ordinary coal-gas produces on an average 5200 heat- 
units, hence 200 litres per hour referred to one second 1 . -^ . -| . 
5200 = 0.29 heat-unit. These correspond to 1208 volt-amperes, 
1 volt-ampere being equal to 0.00024 heat-unit. Hence, in 
Glilcher's thermo-electric pile, which at present produces the 
greatest useful effect, not much more than 1 per cent, of the heat 
is utilized in the entire circuit, and about J per cent, in the outer 
circuit. 

Although thermo-electric piles may be, and are occasionally, 
used for electro-plating operations, they cannot compete with 
dynamo-electric machines driven by steam, which as regards the 
consumption of heat are at least five times more effective. They 
can only be used in place of galvanic batteries, they having the 
advantage of being more convenient to put in operation, more 
simple, cleanly, odorless, and requiring less time for attendance. 
But, on the other hand, their original cost is comparatively large, 
it being ten to twenty times that of Bunsen elements. Thus, 
for instance, Giilcher's thermo-electric pile costs $37.50 in Ger- 
many, to which have to be added $5 for the gas-pressure regulator, 
if required. 



GALVANIC ELEMENTS, THERMOPILES, ETC. 51 

C. Magneto- and Dynamo-electric Machines. 

The principle of induction upon which the dynamo-electric 
machines are based has been explained on p. 21. Faraday, in 1831, 
made the important discovery that by moving a coil of wire in the 
presence of a magnet a current of electricity was generated in 
the coil, or, vice versa, by moving the magnet and holding the coil 
stationary a like result was obtained; thus a current of electricity 
was produced either by moving a wire in the presence of a 
stationary magnet, or by moving a magnet in the presence of a 
stationary wire. 

The intensity of the current thus obtained depends on the 
strength of the magnet and on the velocity with which the mag- 
net or coil is moved through the magnetic field. Upon these 
simple facts is based the whole of the recent important develop- 
ments of electrical science. 

Before describing the various attempts made to devise some 
mechanical means whereby the different elements which produced 
the temporary or momentary currents could be combined, so as 
to collect them, and cause them to flow in rapid succession, the 
one after the other, without interruption, it will be well to re- 
member that the necessary elements for producing these induced 
electric currents are simply a bar magnet and an insulated coil of 
wire. It will also be well to remember that every magnet, no 
matter what its form, has two poles — a north and a south pole — 
and each of these poles exerts a certain influence in its immediate 
neighborhood, the space thus affected being termed the magnetic 
field or the region of the lines of force. The attraction or mag- 
netic force of these lines varies as the inverse ratio of the square 
of the distance ; therefore, the nearer the magnet the greater the 
intensity of the magnetism. Faraday proved that these lines, 
which he designated lines of force, showed by their position the 
direction of the magnetic force, and by their number its intensity. 
By passing a coil of wire through this field, so as to cause it to 
cut, as it were, a number of these lines of force, a current of elec- 
tricity will be generated in the coil ; and if it can be so arranged 
that a number of these coils will pass in rapid succession through 



52 ELECTEO-DEPOSITION OF METALS. 

the magnetic field, we shall have a series of impulses giving us 
practically a continuous stream of electricity. 

Thus a magneto-electric or dynamo-electric machine is simply 
a machine for the conversion of mechanical energy into electri- 
cal energy by means of magneto-electric induction. The term 
dynamo-electric machine is also applied to a machine by means 
of which electrical energy is converted into mechanical energy by 
means of magneto-electric induction. Machines of the latter 
class are generally called motors, those of the former generators. 

Prof. S. P. Thompson defines a dynamo-electric machine as 
follows : — 

" A machine for converting energy in the form of mechanical 
power into energy in the form of electric currents, or, vice versa, 
by the operation of setting conductors (usually in the form of 
coils of copper wire) to rotate in a magnetic field, or by varying 
a magnetic field in the presence of conductors." 

The term dynamo was first applied to such machines because 
of the form in which this machine first appeared, viz., the series- 
wound machine ; it was self-acting, or required no excitement 
other than what it received by the rotation of its armature in the 
field of its magnets, or, indeed, in the field of the earth. 

A dynamo-generator, or a dynamo-electric machine proper, con- 
sists of the following parts : — 

1. The revolving portion, usually the armature, in which the 
electro-motive force is developed which produces the current. 

2. The field magnets which produce the field in which the arma- 
ture revolves. 

3. The pole pieces, or free terminals of the field magnets. 

4. The commutator, by which the currents developed in the 
armature are caused to flow in one and the same direction. In 
alternating machines and in some continuous current dynamos this 
part is called the collector, and does not rectify the currents. 

5. The collecting brushes, that rest on the commutator cylinder 
and take off the current generated in the armature. 

The number of such dynamo machines is legion. In each case 
the arrangement of the armature of the magnets and of the com- 
mutators is varied, but the principle is always the same — coils of 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 53 

insulated wire being caused to cut through magnetic fields, as 
already explaiued. 

The first attempt to devise an electrical machine was made by 
Pixii, who, in 1832, constructed a machine consisting of a perma- 
nent magnet, which he caused to revolve in front of the iron cores 
of a pair of bobbins, forming an electro-magnet. This invention 
was improved by other workers in the field of science, especially 
by Saxton and Clarke, both of whom succeeded in producing very 
useful electric generators, in which the mechanical arrangement is 
the reverse of that in Pixii's — i. e., the magnets are fixed and the 
coils of wire movable. And it is on this plan that all the subse- 
quent machines have been constructed, as affording better results 
than where the coils are stationary and the magnets movable. 

A great improvement was made in 1857, by Dr. W. Siemens, 
of Berlin. It consisted essentially in a new form of armature, 
which, owing to its simplicity and cheapness, is still used for 
many purposes, especially for electro-plating and laboratory 
work. It is composed of a cylinder of iron in which deep longi- 
tudinal grooves are cut resembling in section the letter H. In 
these grooves is wound lengthwise a single coil of wire, the two 
ends of which being joined to a split tube of copper on the axle, 
form the commutator, from which the current is taken off by 
brushes or springs rubbing against it. By this longitudinal arma- 
ture the advantage is gained of cutting the greatest number of 
lines of force when rotated between the poles of a series of 
adjacent magnets. 

One of the most important inventions for the construction of 
electrical machines is the ring conductor by Pacinotti (1860). 
With the use of this ring conductor continuous currents of the 
same direction can be produced without the assistance of a com- 
mutator. 

Next in order comes the important discovery made simulta- 
neously, but independently, by Dr. W. Siemens and Sir C. Wheat- 
stone — a discovery which marks the transition of the magneto- 
electric machine to that type most in practice at present — the 
dynamo machine, failed for convenience the dynamo. What 
Siemens and Wheatstone discovered was this : That a current 
of electricity could be generated in the coils of the armature 



54 ELECTRO-DEPOSITION OF METALS. 

by the feeble residual magnetism in the iron cores of the electro- 
magnets, and that by passing this feeble current round the mag- 
nets their magnetism would be strengthened, which in turn would 
produce a stronger current in the armature, and this current would 
again react on the magnets rendering them more powerful, this 
action going on until the limit of saturation is attained ; for it 
must be understood that this mutual accumulation cannot go on 
indefinitely, the magnetism in the iron cores cannot be intensified 
beyond a certain point, and this point depends on and is con- 
trolled by the scientific conditions on which the machine is con- 
structed. 

Machines constructed on this principle are called, as stated, 
dynamo machines, to distinguish them from those previously used 
in which the magnets were permanently magnetized, thus causing 
the division of electric generators into two great classes, viz., 
magneto and dynamo machines, which are subdivided into two 
varieties — one called the continuous current machine, furnishing 
currents in the same direction, and the other the alternating cur- 
rent machine, wherein the current is rapidly reversed or its direc- 
tion changed many times a minute. 

An essential difference between continuous and alternating cur- 
rent machines is that the former may be self-exciting, whereas the 
latter must have a separate excitor or must be a magneto machine. 
The cores of the electro-magnets, it may be mentioned, are of 
cast-iron, in which there is always a feeble residual magnetism. 
It is also easier to magnetize iron than steel, although, when the 
latter is once magnetized, it retains its magnetism for an indefinite 
period. 

It is not within the province of this work to describe in detail 
all the forms of dynamos, it being sufficient for our purpose to 
discuss those which are adapted to and are used for electro-plating 
uses. If we mention the Gramme machine first, it is not because 
it is superior to other machines, but because M. Gramme, its in- 
ventor, was the first to utilize the idea suggested by Dr. Pacinotti, 
of using an iron ring as a revolving electro-magnet, which, in 
place of having fixed revolving poles, had poles which travelled 
continuously through the whole circumference of the ring. 

Fig. 26 shows the Gramme armature in such a way as to 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



55 



allow its construction to be seen. The core or centre of the 
ring consists of a bunch of soft iron wires; the wire system 



Fig. 26. 




wound about the core is formed of different spools, the initial 
wire of which is soldered to the terminal wire of the neighboring 



Fig. 27. 




spool, so that all the spools of the ring form a single uninterrupted 
conductor. The soldered places lie all on one side of the ring, 



56 



ELECTEO-DEPOSITIOX OF METALS. 



and are fastened to flat copper strips bent at right angles and 
insulated from one another by a non-conducting mass which forms 
the commutator through which the axle passes. The armature 
revolves between the poles of the electro-magnets secured to the 
sides of the machine, as shown in Fig. 27. As the ring is revolved 
a current is generated and flows out with every change in its 
position. The current so made is carried out by wire brushes 
which press upon the terminal plates of the wires in the ring. 

In the modern Gramme dynamos (Fig. 28) for galvano-plastic 
purposes, which have to furnish a considerable volume of current of 




slight electro-motive force, the inducting magnets are surrounded 
by broad copper bands instead of being wound about with copper 
wire, and the armature is built up of stout copper rods, because 
the less resistance the copper windings have the greater the 
volume of current which is produced, while, vice versa, the tension 
increases with their resistance. Hence, machines for electro- 
plating purposes, which have to furnish quantities of current of 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



57 



slight tension, are wound about with stout copper wire, while 
those for illuminating purposes, which must furnish currents of 
high tension, are wound about with thin copper wire. For this 
reason machines constructed for galvano-plastic use and for 
nickelling, coppering, brassing, etc., are not suitable for illumi- 
nating purposes, and, vice versa, machines constructed for electric 
lighting cannot suitably be employed for galvanic purposes. 

A disadvantage of the Gramme machine is that only the portion 
of the copper windings on the outside of the ring conductor is in 
the magnetic field of the poles of the electro-magnets, so that only 
a comparatively small portion of the inductor is exposed to the 
inductive action of the magnets. Hence, in order to furnish cor- 
respondingly strong currents, the ring inductor must revolve very 
rapidly, the three sizes or numbers of Gramme machines mostly 
employed for galvano-plastic purposes making in fact from 1500 
to 2000 revolutions per minute, whereby the bearings are more 
rapidly worn out than with machines running at less speed and, 
besides, more power is consumed. 

Fig. 29.. 




This evil led S. Schuckert, of Nuremberg, to construct a 
machine in which a fat ring is successfully used as an inductor, 
which stands almost entirely under the inductive influence of the 



58 



ELECTRO-DEPOSITION OF METALS. 



electro-magnets. Schuckert's flat ring machine is shown in Fig. 
29. The core of the machine consists of thin sheet ribbands 
insulated one from another, whereby greater solidity is attained ; 
the commutator and brushes are similar to those of the Gramme 
machine. The number of revolutions varies for the different 
sized machines from 500 to 1500 per minute. It is almost noiseless 
in action and is exceedingly well constructed. The formation of 
sparks on the contact-surface of the brushes with the commutator 
is scarcely perceptible, which secures the durability of the latter. 

Fein, of Stuttgart, has endeavored to overcome the defect of 
the Gramme machine in a different manner. In thpse machines 
the polar extensions of the magnets M and 31' (Fig. 30) are elon- 
gated to a sort of drum, A A, which leads into the interior of 
the inductor ring, whereby the greater portion of the windings is 
also brought into the magnetic fields of the electro-magnets. 

Fig. 30. 




Closely resembling the Gramme machine in its general outline, 
but differing materially in construction and action, is that known 
as the Brush dynamo. Its armature, though consisting of a ring 
like that of Gramme's, is, however, differently built up. At 
intervals around the ring a number of transverse grooves are 
formed, in which are wound the coils or bobbins, all in the same 
direction : and instead of forming: a continuous circuit, as in the 



GALVANIC ELEMENTS, THERMO-PILES, ETC. 



59 



Gramme, each diametrically opposite pair of coils is joined to 
each other by one end of each coil, while the other ends of the 
pair (i. e., the ends conveying the current) are connected to the 
commutator. Fig. 31 illustrates the ring, showing the opposite 
coils joined up as described. Four coils are removed to show its 

Fig. 31. 




construction. A series of deep concentric grooves will be ob- 
served formed in the ring, their object being to reduce the mass 




of iron, and also to facilitate ventilation, thereby preventing the 
tendency to heat while the machine is working. 

Fig. 32 represents the complete Brush machine set in motion 



60 



ELECTEO-DEPOSITION OF METALS. 



by a Brotherhood motor with three cylinders, the usual speed of 
the machine beiug about 750 revolutions per minute. 

The machines built by Siemens & Halske, in which the cylin- 
der-inductor invented by Hofner-Altenbeck is used, show a differ- 
ent construction from those previously described. A detailed 
explanation of the cylinder-inductor would lead us too far. It 
consists of a hollow iron cylinder, which revolves with the shaft, 
and about which the wires are wound parallel to the revolving 
axis in such a manner that no wire-windings are in the interior 
of the core (cylinder). The wire spirals wound about the cylin- 
der are divided into sections, which are so connected one with an- 
other as to form a single connected wire conductor. The terminal 
wires of the separate sections are connected to the segments of the 
commutator, so that both the currents generated in the wire sys- 
tem always meet from an opposite direction in two portions of 
the commutator opposite to one another. The commutator is 
constructed according to the Gramme system, and has, of course, 
as many segments as there are sections wound upon the cylinder. 
A real advantage of the machine is that the greater portion of 
the wire-windings of the cylinder-inductor is in the magnetic field. 

Fig. 33. 




Fig. 33 shows a Siemens & Halske magneto-electric machine 
with cylinder-inductor. 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



Gl 



Two series of 25 V-shaped magnets each are placed above and 
below, so that their poles of a similar name are opposite to one 
another, the poles of a similar name of the upper and lower 
magnets being connected one with another by arched pieces of 
soft iron. In the space thus formed between the upper and 
lower magnets, the cylinder-inductor revolves, the generated 
currents being carried away from the commutator by the brushes 
R and R'. 

In Siemens & Halske's dynamo-electric machines for electro- 
metallurgical purposes (Fig. 34) the plate magnets are wound 

Figi 34. 




about with square copper rods, in smaller machines with stout 
copper wire, while instead of spirals the inductor carries copper 
ribbands, which are connected with the commutator by suitably 
bent pieces. 

Fig. 35 shows the Krottlinger machine constructed by Krott- 
linger, of Vienna. It consists of a strong iron base, P, from 
which rise two short cylindrical electro-magnets, M 31, which 
have a semicircular shaft on the upper end N, and closely 
embrace the ring R. The standards L are cast in one piece with 
the base P, and carry the bearings W W. The core of the ring 
R consists of separate disks of cast-iron arranged alongside one 
another upon the shaft so as to form a massive cylinder which is 
wound about with stout copper wire. The inductive spools of 



62 



ELECTRO-DEPOSITION OF METALS. 



the ring are connected by means of screws with the phosphor- 
bronze plates of the commutator C. In this dynamo the current 
generated in the ring does not pass first through the electro-magnets, 




and then as working current into the conductor, but the greater 
portion passes as working current from the brushes B B into the 
conductor to the baths, while the other comparatively smaller 
portion of current passes through the wrappings of the electro- 
magnets MM, and excites them. As in Scbuckert's machines, a 
regulator with resistance coils may be inserted in the circuit of 
the current, which allows of the generation of the current being 
controlled within quite wide limits, as may be desired. The 
advantages of this dynamo consist in the large masses of iron of 
short length with a large cross-section of the cores of the electro- 
magnets, the standards and base being made in one piece, and the 
durable iron core of the ring ; the formation of sparks is slight. 

The Lahmeyer dynamo, shown in Figs. 36, 37, and 38, in cross- 
section, open side view, and perspective exterior view, fulfils the 
three principal conditions of a good dynamo, viz., great useful 
effect, discharge of the current without sparks, and solidity of 
construction. Opposite to the drum-anchor or drum-inductor of 
the machine stand horizontally two short and stout electro-magnet 
cores, whose ends averted from the anchor are connected by a thick 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



63 



iron frame carried above and below around the windings. This 
electro-magnet frame is made of soft cast-iron in one piece with 
the base of the machine, so that no resistance is offered to the 



Fig. 36. 





lines of force by a joint, while the large iron cross-sections also 
give rise to but slight magnetic resistance. 

The magnetic field of the Lahmeyer machine must be consid- 
ered as a magnetic circle in so far as the lines of force which are 
generated by the spools in the iron everywhere contiguous to 
them pass together through both spools, and only ramify outside 
of them in the re-conducting plates B B'. By this favorable 
disposition, a current of slight strength passing through the 
wrappings of the electro-magnets produces a strong excitation of 
the latter. 

The anchor has the shape of the Siemens cylinder, but is com- 
posed of disks of thin, white sheet-iron insulated one from the 
other by paper. Several segments of vulcanized fibre, two of 
which form the face, serve for holding the wrappings of the 
anchor. The latter consists of a single layer of stout copper 
wire, and this, in conjunction with the symmetrical disposition 
which excludes the scattering of the lines of force as much as 
possible, effects a discharge of the current without sparks. The 
space visible in the side view is closed by perforated plates secured 
by screws, as seen in Fig. 38. This is a further advantage of the 
machine in so far that all sensitive parts are protected from external 
injury. Like all cylinder or drum dynamos, the Lahmeyer 
dynamo requires a large number of revolutions per minute, but 



64 



ELECTRO-DEPOSITION OF METALS. 



with the slight weight of the anchor, and the solid construction 
of the bearings, there is but little danger of the rapid wearing 
out of the latter. 



Fig. 38. 




Fig. 39 represents the Weston machine, which is much used 
in this country. Being of small dimensions, of compact form, 
and yielding an abundant current, it is well adapted to the wants 
of the electro-plater. An iron ring or cylinder attached to an 

Fig. 39. 




iron base forms the outer shell of the machine. From the inte- 
rior of this cylinder, and projecting radially towards the centre 



GALVANIC ELEMENTS, THERMOPILES, ETC. 65 

of the apparatus, are arranged a number of magnets (usually five), 
which consist of a core of iron to which are fastened a number of 
thin tempered steel plates, and they are wrapped with insulated 
copper wire and so connected that the poles shall be alternately 
north and south. In the central space left between the inward 
ends of these magnets is arranged a shaft carried by bearings, 
which, to secure greater strength and perfect alignment, are cast 
on the iron disks or heads which are accurately fitted and bolted 
to the ends of the cylinder. To the shaft is secured a series of 
armatures made in segments. The armatures are of iron and also 
wrapped with wire. When revolved the outwardly projecting 
ends of these armatures will pass closely to, but without touching, 
the inwardly projecting ends of the magnets. The commutator 
is made in two pieces, and requires but two springs to carry the 
currents from all the armatures. These springs or brushes are 
clamped in sockets projecting from the front disk of the cylinder. 
An automatic switch or governor is attached to this machine for 
the purpose of preventing it from reversing by the polarization 
of the electrodes. 

The new dynamo electro-plating machine manufactured by the 
Hanson & Van Winkle Co., of Newark, New Jersey, is shown in 
Fig. 40. K is the coil of the field magnet, A the revolving 
armature, and Cthe commutator. BB are the brushes for pick- 
ing up the currents of electricity produced in the armature by re- 
volving in the magnetic field and causing them to flow in one 
direction. The current is not produced by friction. D is the 
lever to adjust the position of the brushes to the commutator. 
IsN are f-inch copper rods from the machine to the tank or to 
the main conductors on the wall. The binding-post on the 
machine marked P is joined to rods connected with the anodes, 
while N is connected to the object rods. The rods on the tank 
should be kept bright with emery paper. When but one tank is 
used, make direct connection in the same way after getting the speed 
of the machine satisfactory for the maximum amount of work. 
The current may be decreased for small surfaces by moving the 
handle of the resistance board from the point marked " strong," 
one segment at a time, until it is found to answer. The position 
of the brushes, as shown in the cut, is the strongest point. By 



6Q 



ELECTRO-DEPOSITION OF METALS. 



moving to the right or left the current is diminished. A slight 
change of position of the brushes is sometimes an advantage in 
setting the brushes when running on large surfaces to avoid 
sparks. 



Fig. 40. 




In using the resistance boards, (see later on) they are put up as 
near the tank as possible — the weak point being used when put- 
ting work in the tank, and then the strength of current is in- 
creased until the power required is obtained. 

The proper current for nickel-plating on brass or other smooth 
surfaces, is when the gas is seen to adhere to the work, and there 
is no tendency to blacken edges. 

The manufacturers of the above-described dynamo machine 
claim for it the following advantages : — 

The field magnets have wrought-iron in them, vastly superior 
to cast-iron. The magnets have a round core, which, for a given 
amount of wire, is much more powerful. They have a very short 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



67 



magnet-circuit. The commutator is easily taken off, so as to re- 
new the segments, which are made of tempered copper, and are 
very durable. The armature and working parts are away from 



Fig. 41. 




68 ELECTRO-DEPOSITION OF METALS. 

the base, and are fully protected from dirt. The field magnets 
are wound on bobbins, and are easily replaced. The armature 
is of Norway iron, each piece being insulated from its neighbor 
and the steel shaft, which entirely dispenses with cross-currents 
and avoids heating of the armature core. 

The same firm also manufactures the bicycle-power plating 
dynamo shown in Fig. 41. This dynamo is a regular machine, 
similar in construction and principle to the preceding larger 
machine. It consists of a dynamo cast upon an iron pedestal, 
with an arm extending for the support of the saddle and hubs 
in which the main bearing runs. The machine has direct poles, 
shortest possible magnetic circuit, and one field coil, giving 
greatest possible amount of magnetism in poles. The field-coil 
is wound upon a bobbin which can be readily taken off. The 
poles have extended arms, which, after being bored and boxed, 
turned to same diameter, and bolted into place, insures perfect 
alignment for bushings in which the armature shaft runs. Every 
part of the machine upon which wear comes is made in duplicate, 
and is easily exchanged for new parts. The machine has a regu- 
lation bicycle saddle with spring adjustments. The saddle post 
is adjustable, allowing a child or the tallest man to do the work 
with perfect satisfaction. The machine is provided with bearing 
rubber pedals, regulation bicycle cranks, and crank-pins. 

This dynamo is intended for work on a small scale, serving as 
a substitute for the battery. With this machine the manufac- 
turers claim that a dozen knives and forks can be plated with a 
triple coating of silver in twenty minutes. A large ice-pitcher 
can be plated in twenty-five minutes, and two dozen spoons in 
twenty minutes. 

The "Improved American Giant" Dynamo, manufactured by 
the Zucker & Levett Chemical Company, of New York, is shown 
in Fig. 42. A is the field magnet, which is built of lamina? of 
the best Swedish iron in the smaller machines and of special cast- 
iron equal to wrought-iron in the larger machines. The laminae 
are stamped out of one piece of iron, thus doing away with all 
joints and consequent magnetic leakage due to that cause. B is 
the base to which the field plates are bolted ; C and C are the 



GALVANIC ELEMENTS, THERMOPILES, ETC. 



69 



brackets which support the armature _D. The bearings supported 
in the brackets are made of the hardest phosphor-bronze and 
are self-oiling. The armature is of an improved Siemens drum 
type, wound and connected so that the coils are perfectly balanced, 




both mechanically and electrically, thus insuring an even distri- 
bution of electro-motive force. 

The core of the armature is built of best Swedish iron, 
thoroughly insulated, to prevent Foucault or eddy currents and 
consequent heating. There is but one turn to every section, and 
each turn consists of a large number of strands of small wires, 
thus facilitating winding and obviating Foucault currents in the 
copper conductors. The heads are covered to prevent oil or dirt 
from entering. 

The commutator having a large number of sections, a perfectly 
even current and deposit are obtained. The commutator-bars 



70 ELECTEO-DEPOSITION OF METALS. 

are drop-forged copper thoroughly insulated with mica through- 
out. 

F and F' are the brushes which collect the current. These 
brushes consist of a very large number of thin copper leaves, 
carefully filed to the proper level, and but a slight tension is re- 
quired. This is easily adjusted with one thumb-screw on the 
brush-holder, which actuates a flat German silver spring, which 
increases or diminishes the tension. 

G are the field magnet Coils which are separately wound on 
iron spools with brass flanges, and then slipped over the cores. 
They are so wound as to prevent the dynamo from reversing, and 
have a comparatively high resistance, thus taking out little energy 
in combination with the extremely low resistance of armature. 
The absence of eddy currents, etc., makes this a most efficient 
machine. 

Detailed descriptions of other machines such as the Miiller, 
Mather, Elmore, Biirgin, Giilcher, etc., would needlessly lengthen 
this chapter. The great impulse which the art of electro-plating 
has within the past decade received is largely due to the great 
improvements that have within this period been made in the con- 
struction of dynamo-electric machines, by which mechanical energy 
generated by the steam-engine or other convenient source of power 
may be directly converted into electrical energy. Without dynamos 
it would be impossible to electro-plate large parts of machines, 
building ornaments, etc., w T hich are thus protected from the influ- 
ence of the weather. They may safely be credited with having 
called into existence an important branch of the electro-plating art, 
viz., nickel-plating, and especially the nickel-plating of zinc sheets 
as well as sheets of copper, brass, steel, and tin, which would have 
been impossible if the manufacturer had to rely upon the genera- 
tion of the electric current by batteries. The latter, at the very 
best, are troublesome to manage ; they only give out their full 
power when freshly charged, and as the chemical actions upon 
which they rely for their power progress, they deteriorate in 
strength and require frequent additions of acids and salts to be 
freshly charged, and their use demands constant vigilance and 
attention. Even when working on a small scale it is cheapest to 



GALVANIC ELEMENTS, THERMOPILES, ETC. 71 

procure a small gas or other motor for driving a small dynamo, 
the lathes, and grinding and polishing machines. 

To make it possible for the manufacturer of dynamos to sug- 
gest the most suitable machine, the following data should be sub- 
mitted to him : — 

1. Variety, size, and number of the baths which are to be fed 
by the machine. 

2. The average surface of the articles in the bath, or their 
maximum surface, and the metals of which they consist. 

3. Whether at one time many and at another time few articles 
are suspended in the bath. 

4. The distance at which the machine can be placed from the 
baths. 

5. The power at disposal. 



72 ELECTRO-DEPOSITION OF METALS. 



IY. 
PRACTICAL PART. 



CHAPTER IV. 

ARRANGEMENT OF ELECTRO-PLATING ESTABLISHMENTS 
IN GENERAL. 

Although rules valid for all cases cannot be given, because 
modifications will be necessary according to the size and extent 
of the establishment, the nature of the articles to be electro-plated, 
and the method of the process itself, there are, nevertheless, cer- 
tain main features which must be taken into consideration in 
arranging every establishment, be it large or small. Only rooms 
with sufficient light should be used, since the eye of the operator 
is severely taxed in judging whether the articles have been thor- 
oughly freed from fat, in recognizing the different tones of color, 
etc. A northern exposure is especially suitable, since otherwise 
the reflection caused by the rays of the sun may exert a disturb- 
ing influence. For large establishments the room containing the 
baths should, besides side-lights, be provided with a sky-light, 
which, according to the location, is to be protected by curtains 
from the rays of the sun. 

Due consideration must be given to the frequent renewal of the 
air in the rooms. Often it cannot be avoided that the operations 
of pickling, etc., must be carried on in the same room in which 
the baths are located. Especially unfavorable in this respect are 
smaller establishments working with batteries, in which the vapors 
evolved from the latter are added to the other vapors, and render 
the atmosphere injurious to health. Hence, if possible, rooms 
should be selected having windows on both sides, so that by 
opening them the air can at any time be renewed, or the baths 
and batteries should be placed in rooms provided with chimneys ; 



ELECTRO-PLATING ESTABLISHMENTS. 73 

by cutting holes of sufficient size in the chimneys near the ceilings 
of the rooms the discharge of injurious vapors will in most cases 
be satisfactorily effected. 

To those working with Bunsen elements, it is recommended to 
place them in a closet varnished with asphalt or ebonite lacquer, 
a:id provided with lock and key. The upper portion of the closet 
should communicate by means of a tight wooden flue with a 
chimney or the open air. 

Since the baths work with greater difficulty, slower and more 
irregular below a certain temperature, provision for the sufficient 
heating of the operating rooms must be made. Except baths 
for hot gilding, platinizing, etc., the average temperature of the 
plating solutions should be from 64.5° to 68° F., at which they 
work best ; it should never be below 59° F., for reasons to be 
explained later on. Hence, for large operating rooms such heat- 
ing arrangements must be made that the temperature of the baths 
cannot fall below the minimum even during the night, otherwise 
provision for the ready restoration of the normal temperature at 
the commencement of the work in the morning has to be made. 
Rooms heated during the day with waste steam from the engine, 
generally so keep the baths during the winter — the only season 
of the year under consideration — that they show in the evening 
a temperature of 64.5° to 68° F., and if the room is not too 
much exposed, the temperature, especially of large baths, will 
only in rare cases be below 59° F. For greater security the heat- 
ing pipes may be placed in the neighborhood of the baths ; if 
this should not suffice to protect the baths from cooling off too 
much, it is advisable to locate in the operating room a steam con- 
duit of small cross-section fed from the boiler and to pass steam 
for a few minutes through a coil of metal indifferent to the 
plating solution suspended in the bath. In this manner baths of 
1000 quarts, which, on account of several days' interruption in 
the operation had cooled to 36° F., were in ten minutes heated to 
68° F. For smaller baths it is better to bring a small portion of 
them in a suitable vessel to the boiling-point, over a gas flame, 
and adding it to the cold bath, and if, after mixing, the tempera- 
ture of the bath is still too low, repeating the operation. 

Another important factor for the operating rooms is the con- 



74 ELECTRO-DEPOSITION OE METALS. 

venient renewal of the waters required for rinsing and cleansing. 
Without water the electro-deposition of metals is impossible ; the 
success of the process depends in the first place on the careful 
cleansing of the metallic articles to be electro-plated, and for that 
purpose water, nay, much water, hot and cold, is required, as 
will be seen in the " preparation of the articles." Large estab- 
lishments should, therefore, be provided with pipes for the admis- 
sion and discharge of water, one conduit terminating as a rose 
over the table where the articles are freed from grease. In 
smaller establishments, where the introduction of a system of 
water-pipes would be too expensive, provision must be made for 
the frequent renewal of the cleansing water in the various vats. 

In consequence of rinsing and transporting the wet articles to 
the baths much moisture collects upon the floor of the operating 
rooms. The best material for floors of large rooms is asphalt, it 
being, when moist, less slippery than cement ; a pavement of 
brick or mosaic laid in cement is also suitable, but has the disad- 
vantage of cooling very much. The pavement of asphalt or 
cement should have a slight inclination, a collecting basin being 
located at the lowest point, which also serves for the reception of 
the rinsing water. Wood floors cannot be recommended, at least 
for large establishments, since the constant moisture causes the 
wood to rot ; however, where their use cannot be avoided, the 
places where water is most likely to collect, should be strewn with 
sand or saw-dust, frequently renewed, or the articles when taken 
from the rinsing water or bath be conveyed to the next operation 
in small wooden buckets or other suitable vessels. 

The operating room should be of such a size as to permit the 
convenient execution of the necessary manipulations. Of course, 
no general rule can be laid down in this respect, as the size of the 
room required depends on the number of the processes to be 
executed in it, the size and number of articles to be electro-plated 
daily, or within a certain time, etc. However, there must be 
sufficient room for the batteries or dynamo, for the various baths, 
between which there should be a passage-way at least twenty inches 
wide, for the table where the articles are freed from grease, for the 
lye kettle, hot- water reservoir, saw-dust receptacle, tables for 
tying the articles to hooks, etc. 



ELECTRO-PLATING ESTABLISHMENTS. iO 

The rooms used for grinding, polishing, etc., also require a good 
light in order to enable the grinder to see whether the article is 
ground perfectly clean, and all the scratches from the first grind- 
ing are removed. Where iron or other hard metals are ground 
with emery, it is advisable to do the polishiug in a room sepa- 
rated from the grinding shop by a close board partition, because 
in the preparatory grinding with emery, which is done dry, with- 
out the use of oil or tallow, the air is impregnated with fine 
particles of emery, which settle upon the polishing disks and 
materials, and in polishing soft metals cause fine scratches and 
fissures injurious to the appearance of the articles and difficult to 
remove by polishing. Hence, all operations requiring the use of 
emery, or coarse grinding powders, should be performed in the 
actual grinding- room, as well as the grinding upon stones and 
scratch-brushing by means of rapidly revolving steel scratch- 
brushes of iron castings. Articles already electro-plated are, of 
course, scratch -brushed in the plating-room itself, either on the 
table used for freeing the articles from grease, or on a bench 
especially provided for the purpose. In the polishing room are 
only placed the actual polishing machines, which by means of 
rapidly revolving disks of felt, flannel, etc., and the use of polish- 
ing powders, or polishing compositions, impart to the articles the 
final lustre before and after electro-plating. The formation of 
dust in the polishing rooms is generally over-estimated ; it is, 
however, sufficiently serious to render their separation by a close 
partition from the electro-plaing room necessary, otherwise the 
polishing dust might settle upon the baths and give rise to 
various disturbing phenomena. In rooms in which large surfaces 
are polished with Vienna lime, as, for instance, nickelled sheets, 
the dust often seriously affects the health of the polishers, especi- 
ally in badly ventilated rooms, and in such cases it is advisable to 
provide an effective ventilator. If this cannot be done, wooden 
frames covered with packing-cloth, placed opposite the polishing 
disks, render good service ; the packing- cloth, by being fre- 
quently moistened, retaining a large portion of the polishing 
dust. 

For grinding lathes requiring the belt to be thrown off in order 
to change the grinding, it is best to place the transmission carrying 



76 ELECTRO-DEPOSITION OF METALS. 

the belt-pulleys at a distance of about three feet from the floor, 
for lathes with spindles outside the bearings the transmission 
may be on the ceiling or wall. The revolving direction of the 
principal transmission should be such as to render the crossing of 
the belts to the grinding and polishing machines unnecessary, 
otherwise the belts on account of the great speed will rapidly 
wear out. 

ELECTRO-PLATING ARRANGEMENTS IN PARTICULAR. 

The actual electro-plating plant consists of the following parts : 
1. The sources of current (batteries or dynamo-electric machines) 
with auxiliary apparatus. 2. The current-conductors 3. The 
baths, consisting of the vats, the plating solution, the anodes, 
and the conducting rods with their binding-screws. 4. The 
apparatuses for cleansing, rinsing, and drying. The sources of 
current have already been discussed in Chap. III. p. 29, and the 
laws governing the suitable coupling of the elements on p. 17. 

A. Arrangement with elements. — In working with elements it 
is first necessary to have a clear idea of the area of the articles 
which are to be at one time electro-plated in a bath, and of the 
magnitude of the resistance opposed by the bath to the current. 
This and the size of the anodes show how many elements must be 
put together for a battery, and how the elements are to be coupled. 
Suppose we have a nickel bath which requires for its decomposi- 
tion a current of 2.5 volts of electro-motive force or tension ; now 
since, according to p. 36, a Bunsen element yields a current of 
1.88 volts, the reduction of the nickel cannot be effected with one 
such element, but two elements must be coupled for tension one after 
the other, whereby, leaving the conducting resistance of the wires 
out of consideration, an electro-motive force or tension of 2 x 1.88 = 
3.76 volts is obtained, with which the decomposition of the solu- 
tion can be effected. If, on the other hand, we have a silver bath 
which requires only ^ volt for its decomposition, we do not couple 
two elements one after the other, because the electro-motive force 
of a single element suffices for the reduction of the silver. On 
p. 17 it has been seen that by coupling the elements one after the 
other (coupling for tension) the electro-motive force of the battery 



ELECTRO-PLATING ESTABLISHMENTS. 



77 



is increased, but the quantity of current is not increased, and that 
to attain the latter the elements must be coupled alongside of one 
another (coupled for quantity). Hence in a group of, for instance, 
three elements coupled one after another, only one single zinc 
surface of the elements can be considered effective in regard to 
the quantity of current. Now, the larger the area of articles at 
the same time suspended in the bath is, the greater the number of 
such effective zinc surfaces of the group of elements to be brought 
into action must be, and, if for baths with medium resistance, it 
may be laid down as a rule that the effective zinc surface must 
be at least as large as the area of the articles, provided the surface 
of the anodes is at least equal to the latter, the approximate num- 
ber of elements and their coupling for a bath can be readily found. 
Let us take the nickel bath, which, as above mentioned, requires 
a current of 2.5 volts, and for the decomposition of which two 
elements must, therefore, be coupled one after the other, and sup- 
pose that the zinc surface of the Bunsen elements is 500 square 
centimetres, then the effective zinc surface of the two elements 
coupled one after the other will also be 500 square centimetres ; 
hence a brass sheet 20 x 25 = 500 centimetres can be conveniently 
nickelled on one side with these two elements, or a sheet 10x25 = 
250 centimetres on both sides. Now suppose the surface to be 
nickelled were twice as large, then the two elements would not 

Fig. 43. 




suffice, and a second group of two elements, coupled one after the 
other, would have to be joined to the first group for quantity as 
shown in Fig. 4, or perspectively in Fig. 43. Three times the 
object surface would require three groups of elements, and so on. 



78 ELECTRO-DEPOSITION OF METALS. 

In giving these illustrations it is supposed the objects are to 
have a thick solid plating ; for rapid plating with a thin deposit 
a different course has to be followed. Only a slight excess of 
electro-motive force in proportion to the resistance of the bath 
being in the above-mentioned case present, reduction takes place 
slowly and uniformly without violent evolution of gas on the 
objects, and by the process thus conducted the deposit formed is 
sure to be homogeneous and dense, since it absorbs but slight 
quantities of hydrogen, and in most cases it can be obtained of 
sufficient thickness to be thoroughly resistant. If, however, the 
operation is to be executed quickly and without regard to great 
solidity and thickness of the deposit, the elements have to be 
coupled so that the electro- motive force is sufficiently large for 
the current to readily overcome the resistance of the bath. This 
is attained by coupling three, four, or more elements one after the 
other, as shown in the scheme Fig. 2. However, such deposits 
can never be homogeneous, because they condense and retain 
relatively large quantities of hydrogen. 

As regards the filling and other management of the batteries, the 
reader is referred to pp. 34-39, under Bunsen elements. Having 
seen how many elements are required, and how they have to be 
coupled to form a battery for certain purposes, we will next con- 
sider the auxiliary apparatuses. 

Only in very rare cases will it be possible to always charge a 
bath or several baths with the same object-area ; and according 
to the amount of business, or the preparation of the objects by 
grinding, polishing, and pickling, at one time large, and at another 
small, areas will be suspended in the bath. jNow, suppose a battery 
suitable for a correct deposit upon an area of, say five square feet, 
has been grouped together ; and, after emptying the bath, a charge 
only half as large is introduced, the current of the battery will, 
of course, be too strong for this reduced area, and there will be 
danger of the deposit not being homogeneous and dense, but form- 
ing with a crystalline structure, the consequence of which, in most 
cases, will be slight adhesiveness, if not absolute uselessness. 
With sufficient attention the total spoiling of the articles might 
be prevented by removing the objects more quickly from the bath. 
But this is groping in the dark, the objects being either taken too 



ELECTRO-PLATING ESTABLISHMENTS. 



79 



soon from the bath, when not sufficiently plated, or too late, when 
the deposit already shows the consequences of too strong a current. 
To control the current an instrument called the rheostat, cur- 
rent-regulator, resistance board, or switch board, has been con- 
structed, which allows of the current-strength of a battery being 
reduced without the necessity of uncoupling elements. It is evi- 
dent that the current of a battery, if too strong, can be weakened 
by decreasing the number of elements forming the battery, and 
also by decreasing the surface of the anodes, because the external 
resistance is thereby increased. This coupling and uncoupling of 
elements is, however, not only a time-consuming, but also a dis- 
agreeable labor ; and it is best to use a resistance board, with 
which by the turn of a handle, the desired end is attained. Figs. 
44 and 45 show this instrument. Its action is based upon the 



Fig. 44. 



Fig. 45. 





TbtheJBatf) 



TotheBctth. 



.following conditions : As explained on p. 19, the maximum per- 
formance of a battery takes place when the external resistance is 
equal to the internal resistance of the battery. By increasing the 
external resistance, the performance is decreased, and a current of 
less intensity will pass into the bath when resistances are placed 
in the circuit. The longer and thinner the conducting wire is, 
and the less conducting power it possesses, the greater will be the 
resistance which it opposes to the current. Hence, the resistance 
board consists of metallic spirals which lengthen the circuit, con- 



80 ELECTRO-DEPOSITION OF METALS. 

tract it by a smaller cross-section, and by the nature of the 
metallic wire have a resistance-producing effect. For a slight re- 
duction of the current, copper spirals of various cross-sections are 
taken, which are succeeded by brass spirals, and finally by Ger- 
man silver spirals, whose resistance is eleven times greater than 
that of copper spirals of the same length and cross-section. In 
Fig. 44 the conducting wire coming from the battery goes to the 
screw on the left side of the resistance board, which is connected 
by stout copper wire with the first contact-button on the left ; 
hence by placing the metallic handle upon the button furthest to 
the left, the current passes the handle without being reduced, and 
flows off through the conducting wire secured in the setting-screw 
of the handle. By placing the handle upon the next contact- 
button, to the right, two copper spirals are brought into the cir- 
cuit ; by turning the handle to the next button four spirals are 
brought into the circuit, and so on. By a choice of the cross- 
sections of the spirals, their length and the metal of which they 
are made, the current may be more or less reduced as desired. 

To control the reduction of the current effected by the resist- 
ance, a galvanometer is placed behind it. It consists of a mag- 
netic needle oscillating upon a pin, below which the current is 
conducted through a strip of copper, or, with weaker currents, 
through several coils of wire. The electric current deflects the 
magnetic needle from its position, and the more so the stronger 
the current is ; hence the current-strength of the battery can be 
determined by the greater or smaller deflection. 

For a weak current, such as, for instance, that yielded by two 

elements, it is of advantage to use a horizontal galvanometer (Fig. 

46). It is screwed to a table by means of 

g ' a few brass screws in such a position that 

the needle in the north position, which it 

occupies, points to 0° when no current 

passes through the instrument. Articles 

of iron and steel must, of course, be kept 

away from the instrument. For stronger 

currents, it is better to combine a vertical galvanometer with the 

resistance board and fasten it to the same frame as shown in Fig. 

45. The screw of the handle of the resistance board is connected 




ELECTRO-PLATING ESTABLISHMENTS. 



81 



with one end of the copper strip of the vertical galvanometer, 
while the other is connected with the screw on the right side of 
the resistance board in which is secured the wire leading to the 
bath. The resistance board and galvanometer are placed in one 
conducting wire only, either in that of the anodes or of the objects ; 
one of these wires is simply cut, and the end connected to the 
battery is secured in the setting-screw on the side of the resist- 
ance board marked " strong," while the other end which is in con- 
nection with the bath is secured in the setting-screw on the oppo- 
site side marked " weak." The entire arrangement will be per- 
fectly understood from Figs. 47 and 50. 



Fig. 47. 




DC 



r&~ 



Figs. 48 and 49 show two rheostats patented and manufactured 
by the Hanson & Van Winkle Company, of Newark, N. J. In 
Fig. 48, the spiral EE'm a ribbon of German silver of various thick- 
nesses depending on the size of dynamo or size of tank. When 
the lever D is moved to the right, the contact-piece in connection 
with a flexible covered copper cable is moved towards the centre 
or point of maximum power. When this is moved to the left, 
there is an increase of resistance until the end of the spiral is 
reached. The position of the contact-piece is shown midway. As 
will be seen, the movement is under perfect control, and is con- 
6 



82 



ELECTRO-DEPOSITION OF METALS. 



tinuons without any sudden fluctuation of power. The connec- 
tion A is connected with rod to one pole of the dynamo, and con- 
nection B to the anode rod of the tank. C is the galvanometer. 




An improved rheostat shown in Fig. 49 is adapted for the 
smallest currents and tanks up to the largest currents and 
surfaces. It is manufactured by the same firm. 

As is well known, different voltages are employed to operate 
different solutions. It is required of the electro-plating dynamo 
that a voltage sufficiently great be generated to do the work in a 
solution that is of the highest resistance, and at the same time 
deposit in low resistance solutions. Then again the voltage has 



ELECTRO-PLATING ESTABLISHMENTS. 



83 



to be great enough to overcome the resistance of the conductors 
to the various tanks, which frequently is unnecessarily great. 
The tank nearest the dynamo, with the customary method, 
receives the most current, and a tendency to burn and blacken is 
noticed in a marked degree. When metals such as silver and cop- 
per are to be deposited in connection with such metals as nickel and 
brass, requiring a higher electro-motive force, a considerable drop 
in voltage is demanded in the lower resistance solutions, so as not to 
blacken the work. With the ordinary style of resistance board, 
this is done at a great loss of current and work capacity of tank. 

Fig. 49. 




When a tank is being filled with work, with the improved 
rheostat in circuit, the current can be entirely cut off, or partially 
left on, as may be desired. When the tank is full the current 
can be switched on, and with this rheostat sufficient current mav 
be conveyed to the work in the fastest manner. With old resist- 
ance boards about the greatest carrying capacity that they will 
feed is from 25 to 35 amperes, and never over 35 amperes, the 
reason for this deficiency being the smallness of the resistance 



84 ELECTEO-DEPOSITTOX OF METALS. 

wire, insufficient metal-conductivity, combustible material for 
backing, etc. It is necessary to have some resistance in the cir- 
cuit, so as not to blacken the work. With the improved rheostat, 
three times the current can be conveyed without showing heat in 
the least, in any part of the same, the resistance-wires, segments, 
switch or base-plate. 

If, with the old style of resistance boards, more than 35 
amperes are to be carried, the wire gets too hot, warps out of 
shape, and burns out the back or base-board, which is of wood 
or other combustible material, blues over and melts out segments, 
etc. With the improved rheostat all this is overcome, it being 
constructed upon scientific principles, with large heavy copper 
segments having great carrying capacity, with a most solid 
switch held against segments, with heavy, strong spiral springs, 
firmly held down with two nuts, all mounted upon a cast-iron 
base-plate, insulated entirely with non-combustible material. 

This rheostat is claimed by the manufacturers to have twice 
the carrying capacity of any resistance board ever made for this 
purpose, it having at the same time sufficient length of wire to 
allow of toning down the highest electro- motive force used in 
electro-plating to the lowest degree that is ever called for, without 
showing heat or any unfavorable symptoms. It is further claimed 
that by the use of this rheostat any plating-room using two or 
more tanks can be doubled in capacity, provided the dynamo has 
the current-capacity. The old-style boards have, as a rule, plenty 
of resistance for small work, but not the carrying capacity to 
allow sufficient amperes to pass to do the work that a tank is 
capable of. 

This improved rheostat is manufactured in various sizes and 
capacities (Nos. 1 to 7) by the Hanson & Van Winkle Co., of 
Newark, N. J., at prices varying from $10 to $40. Nos. 1 , 2, and 
3 are suitable for controlling the shunt-field of the dyuamos 
manufactured by the same firm, also for small tanks ; No. 4 is 
suitable for controlling large dynamos in their shunt, and 
medium-size tanks; No. 5 is suitable for controlling the ordi- 
nary size tanks that are in most general use ; No. 6 is suitable for 
extra large size tanks, and No. 7 for controlling main line currents 
and groups of tanks. 



ELECTRO-PLATING ESTABLISHMENTS. 



85 



Having discussed the advantages derived from the use of the 
resistance board, it remains to add a few words regarding the in- 
dications made by the galvanometer. Since the greater deflection 
of the needle depends, on the one hand, on the greater current- 
strength, and, on the other, on the slighter resistance of the outer 
closing arc (conducting wires, baths, and anodes), it is evident 
that a bath with slighter resistance, when worked with the same 
battery and containing the same area of anodes and objects, will 
cause the needle to deflect more than a bath of greater resistance 
under otherwise equal conditions. Hence the deductions drawn 
from the position of the needle for the electro-plating process are 
valid only for determined baths and determined equal conditions, 
but with due consideration of these conditions are of great value. 
Suppose a nickel bath always works with the same area of objects 

Fig. 50. 




and of anodes, and experiments have shown that the suitable cur- 
rent-strength for nickelling this area of objects is that at which the 
needle stands at 15° ; and suppose further that the battery has 
been freshly filled and causes the needle to deflect to 25°, then 
the handle of the resistance board will have to be turned so far 
to the right that the needle, in consequence of the introduced re- 
sistances, returns to 15°. Now if, after working for some time, 



86 ELECTRO-DEPOSITION OF METALS. 

the battery yields a weaker current, the needle, since the resistance 
remains the same, will constantly retrograde, and has to be brought 
back to 15° by turning the handle to the left, when a current of 
equal strength of the former will again flow into the bath. This 
play is repeated until finally the handle stands upon the button 
furthest to the left, at which position the current flows directly 
into the bath without being influenced by the resistances of the 
resistance board. If now the needle retrogrades below 15°, it is 
an indication to the operator that he must renew the filling of the 
battery if he does not prefer suspending fewer objects in the bath. 
For this reduced object-area it is no longer required for the needle 
to stand at 15° in order to warrant a correct progress of the gal- 
vanic process, since the resistance being in this case greater, a de- 
flection to 10°, or still less may suffice. This illustration will 
sufficiently show that the current-indication by the galvanometer 
is not and cannot be absolute, but that the deductions must always 
be drawn with due consideration to the conditions — area of objects 
and of anodes, and distance between them. An operator to be sure 
in this respect, and, above all, wishing to work scientifically, will 
replace the galvanometer by a voltmeter, which indicates the abso- 
lute magnitude of the electro-motive force passing into the bath, 
as will be explained later on. 

It frequently happens that in consequence of defective contacts 
with the binding-screws of the battery, or by the conductors of 
the objects and of the anodes touching one another (short circuit 
with non-insulated conducting wires), no current whatever flows 
into the bath. Such an occurrence is immediately indicated by 
the galvanometer, the needle being not at all deflected in the first 
case, while in the latter the deflection will be entirely different 
from the usual one. The magnetic needle of the galvanometer 
also furnishes a means of recognizing the polarity of the current. 
If the galvanometer be placed in the positive conductor by secur- 
ing the wire coming from the battery in the binding-screw on the 
south pole of the galvanometer, and the wire leading to the bath 
in the binding-screw on the north pole of the needle, the needle, 
according to Ampere's law, will be deflected in the direction of 
the hands of a watch, i. e., to the right if the observer stands so 
in front of the galvanometer as to look from the south pole 



ELECTRO-PLATING ESTABLISHMENTS. 87 

towards the north pole, because the battery current flows out 
from the positive pole through the conducting wire, anodes, and 
fluid to the objects, and from these back through the object wire 
to the negative pole of the battery. If now in consequence of 
the counter-current formed in the bath by the metallic surfaces of 
dissimilar nature (see later on), and flowing in an opposite direc- 
tion to that of the battery-current, the latter is weakened, the 
needle will constantly further retrograde from the zero point, and 
when the counter or polarizing current becomes stronger than the 
battery-current, it will be deflected in an opposite direction as be- 
fore. Hence, by observing the galvanometer the operator can 
avoid the annoying consequences of polarization, which will be 
further discussed under nickelling. 

From what has been said in this chapter and in the theoretical 
part, it is self-evident what rules have to be observed in conduct- 
ing the current. Since the current-strength is weakened by re- 
sistance, the cross-section of the current-carrying wire as well as 
of that leading to the objects and to the anodes must be of a size 
corresponding to the current-strength, and the material for the 
wires should possess as high a conducting power as possible. 
Chemically pure copper is best suited for this purpose. Some in- 
formation for calculating the thickness of the wires will be found 
at the end of the section " Arrangement with dynamo machines." 

The positive or anode wire effects the connection between the 
anodes of the bath and the positive pole (anode or carbon pole) 
of the battery, while the negative or object wire brings the objects 
in the bath into metallic contact with the negative (zinc) pole of 
the battery. As previously mentioned, the resistance board with 
galvanometer is placed in one or the other of the wires. 

For conducting the electric current to the baths, metallic wires, 
bands, spirals, or ribbons are used. The conducting wires are 
either employed in their natural metallic state, or are covered 
with some insulating or poorly conducting substance, such as 
cotton, silk, India-rubber, gutta-percha, and various varnishes. 
It is evident that covered wires should be bare and clean at their 
extremities where they are connected with the battery and with 
the anodes and objects to be plated. Wires of pure, well-annealed 
copper possess the best conducting power, and should have a sec- 



88 



ELECTRO-DEPOSITION OF METALS. 



tional area capable of carrying the maximum quantity of current 
without offering appreciable resistance. Cables should be chosen 
where a large volume of current must be carried, they being more 
flexible than wire of a large size, and can be more easily laid. 

Insulated wires may come in contact with each other without 
inconvenience. Such, however, is not the case with bare wires ; 
because the electricity will pass through the shortest circuit and 
will not go through the bath if the two wires are in metallic con- 
tact. Such contact should, therefore be carefully avoided. 

Vats or tanks. — These are the vessels to hold the plating solutions. 
Their shape may be either circular, square, or rectangular. They 
should be perfectly tight, impervious to the solutions, and unacted 
upon by them. They are made of different materials — stoneware, 
glass, or porcelain vats being best, but they are the most fragile 
and expensive. 

Wooden vats must be carefully constructed, and are best secured 
at the ends by bolts and nuts, as shown in Fig. 51, which serve 
to hold the sides firmly against the end pieces. The vat is then 

Fig. 51. 




coated with a mixture of equal parts of pitch and rosin boiled 
with a small quantity of linseed oil. Another mixture, which has 
been found to afford a good protective covering to wood, consists 
of 10 parts of gutta-percha, 3 of pitch, and 1J each of stearin and 
linseed oil, melted together and incorporated. 

For large baths containing potassium cyanide holders of bricks 



ELECTRO-PLATING ESTABLISHMENTS. 



89 



laid in cement may also be used, or holders of boiler-plate lined 
inside with a layer of cement. 

As an all-round useful vat there is nothing equal to one of en- 
amelled iron such as is shown in Fig. 52. It is enamelled with a 
white acid-proof enamel and is highly recommended for all solu- 

Ffc. 52. 




tions. It is made in other shapes and sizes up to 5| feet long, 24 
inches wide, and 19 inches deep, and can be obtained from the 
Hanson & Van Winkle Company, of Newark, N. J., and other 
dealers in electro-plating materials. 

Fig. 53 shows an agate vessel for gold and other solutions. 
This material stands cyanide solutions, acids, etc. 

Fig. 53. 




The vats for heating baths are best made of enamelled iron or 
wood lined with sheet lead ; stoneware vats do not bear heating. 

It is advantageous to provide the narrow sides of the vats with 
semi-circular notches for the conducting rods to rest in to prevent 
their rolling away. When using stoneware vats the conducting 
rods are laid directly upon the vats ; vats of other material must 
be provided with an insulated rim of wood, or the rods are insu- 



90 



ELECTRO-DEPOSITION OF METALS. 



lated by pushing a piece of rubber hose over their ends. Accord- 
ing to the size of the bath, 3, 5, 7, or more conducting rods, best 
of pure massive copper, are used. 

To secure the uniform coating of the objects with metal they 
must be surrounded as much as possible by anodes, i. e., the 
positive pole plates of the metal which is to be deposited. For 

Fig. 54. 




flat objects it suffices to suspend them between two parallel rows 
of anodes, the most common arrangement being to place three rods 



ELECTRO-PLATING ESTABLISHMENTS. 



91 



across the bath, the two outermost of which carry the anodes, 
while the objects are secured to the centre rod. For wide baths 
five conducting rods are frequently used, but they should always 
be so arranged that a row of objects is between two rows of 
anodes. The arrangement frequently seen with four rods across 
the baths, of which the outermost carry anodes, and the other 
two objects, is irrational if the objects are to be uniformly plated 
on all sides, because the sides turned towards the anodes are 
coated more strongly than those suspended opposite to the other 
row of objects. 

For large round objects it is better to entirely surround them 
with anodes, if it is not preferred to turn them frequently, so that 
all sides and portions gradually feel the effect of the immediate 
neighborhood of the anodes. (See " Nickelling.") 

For objects to be plated on one side only the centre rod may 
be used for the anodes, and the two outer ones for the objects ; 
the surface to be plated being, of course, turned towards the 
anodes. 

The rods carrying the anodes, as well as those carrying the ob- 
jects, must be well connected with each other, which is effected by 
means of binding posts and screws of the forms shown in Fig. 
54, Nos. 1 and 2 being rod connections for tanks ; No. 3 a wire 
connection for cutting-in branch between batteries or dynamos 
and tanks ; No. 4, wire connection for two or more wires, and 
No. 5, binding-post for resistance board or dynamo. 

The anodes are suspended from the cross rods by strong hooks 
of the same metal, so that they can be entirely immersed in the 
bath (Fig. 55) ; hooks of another soluble 
metal would contaminate the bath by dis- 
solving in it, and this must be strictly 
avoided, as it would cause all sorts of dis- 
turbances in the correct working of the 
bath. In case hooks of another metal, 
except platinum, are used, the anodes 
must be hung so that they project above 
the surface of the liquid, and the hooks 
not being immersed are, therefore, not 
liable to corrosion ; but the anodes are 



Fig. 55. 



Fisr. 56. 




92 ELECTRO-DEPOSITION OF METALS. 

then not completely used up, the portion dipping into the solution 
being gradually dissolved, whilst the portion projecting above the 
fluid remains intact. Instead of wire hooks, strips of the same 
metal as the anodes and fastened to them by a rivet may also be 
used (Fig. 56). 

For suspending the objects lengths of soft pure copper wire, 
technically called slinging wires, are used. They are simply suit- 
able lengths of copper wire of a gauge to suit the work in hand, 
wire of No. 20 Birmingham wire gauge (see Chapter XVIII., 
" Useful Tables") being generally employed for such light work 
as spoons, forks, and table utensils. Wire of a larger diameter 
should be employed for large and heavy goods. The immersed 
ends of these wires becoming coated with the metal which is be- 
ing deposited, they should be carefully set aside each time after 
use, and when the deposit gets thick it should be stripped off in 
stripping acid, and the wire afterwards annealed and straightened 
for future use. 

To keep the rods clean and to protect them from the fluid drain- 
ing off from the articles when taken from the bath, it is advisable 
to cover them with a roof of strips of wood ( /\ ), or a semi- 
circular strip of zinc coated with ebonite lacquer ; by this means 
the frequent scouring of the rods, which otherwise is necessary in 
order to secure a good contact with the hooks of the anodes, is 
done away with. 

The plating solutions, briefly called baths, will be especially 
discussed in speaking of the various electro-plating processes. It 
still remains to consider the cleansing and rinsing apparatuses. 
Every electro-plating establishment, no matter how small, re- 
quires at least one tub or vat in which the objects can be rubbed 
or brushed with a suitable agent in order to free them from 
grease. This is generally done by placing a small kettle or 
stoneware pot containing the cleansing material at the right-hand 
side of the operator alongside the vat or tub. Across the latter, 
which is half filled with water, is laid a board of soft wood 
covered with cloth, which serves as a rest for the objects pre- 
viously tied to wires. The objects are then scrubbed with a 
brush or rubbed with a piece of cloth dipped in the cleansing 
agent. The latter is then removed by rinsing the objects in the 



ELECTRO-PLATING ESTABLISHMENTS. 93 

water in the tub and drawing them through water in another tub. 
By this cleansing process a thin film of oxide is formed upon the 
metals, which would be an impediment to the intimate union ot 
the electro-deposit with the basis-metal. This film of oxide has 
to be removed by dipping or pickling, for which purpose another 
vat or tub containing the pickle, the composition of which varies 
according to the nature of the metal, has to be provided. After 
dipping, the objects have to be again thoroughly rinsed in water 
to free them from adhering pickle, so that for the preparatory 
cleansing processes three vessels with water, which has to be fre- 
quently renewed, as well as the necessary pots for pickling solu- 
tions, have to be provided. In case the vat for cleansing the arti- 
cles or the box-like table (see Fig. 62) is provided with a rose-jet, 
under which the objects are rinsed, the other vats are not required. 

After having received the electro-deposit the objects have to 
be again rinsed in cold water, which can be done in one of the 
three vats or with the rose-jet, and finally have to be immersed in 
hot water until they have acquired the temperature of the latter. 
How the water is heated makes no difference, and depends on the 
size of the establishment. The heated objects are then imme- 
diately dried in a box filled with dry, fine sawdust — that of 
maple, poplar, or other wood free from tannin being suitable for 
the purpose. 

B. Arrangements with dynamo-electric machines. — For setting up 
and running the machines the following rules are to be observed. 
Larger machines are to be screwed to square wooden joists resting 
upon a solid brick foundation about six inches above the floor ; 
smaller machines may be placed upon and fastened to strong 
tables secured to the floor or wall. The principal point is that the 
foundation or table is not subjected to shocks which would be 
transferred to the machines and cause, by the vibration of the 
brushes, a larger formation of sparks, and consequent greater 
wear of certain portions of the machine. Foundations about 8 
inches wider on each side than the machine and built of brick and 
cement have been found most suitable. If possible, the machines 
should be located in the neighborhood of the baths they are to 
feed, since the greater the distance from the bath at which they 
are placed the larger the cross-section of the principal conducting 



94 ELECTRO-DEPOSITION OF METALS. 

wire must be, and the more troublesome the regulation of the 
current will prove, provided it is not intended to place another 
resistance board just in front of the bath, which is the best plan 
for regulating the current with the greatest nicety. 

It is best to set the dynamo in motion by means of a gearing 
with loose and fast pulley so as to render a gentle engaging of 
the machine possible, and not directly from the fly-wheel of the 
motor, whereby in consequence of the jumping and dragging of 
the belt it is apt to run less regularly. The bearings should be 
kept well lubricated, best with automatic oilers filled with good 
lubricating oil. The stated number of revolutions per minute 
should not be exceeded, since by the stronger current thereby 
generated the machine might become very hot and suffer injury. 
On the other hand, when a weaker current is required, the machine 
may be run more slowly than the maximum performance with the 
prescribed number of revolutions. The brushes which conduct 
the current from the commutator should be firmly secured in their 
holders by means of screws, and the levers pressing them by 
means of spiral springs against the commutators must be fixed 
so that the brushes securely and uniformly slide upon them ; 
pressing the brushes too tightly against the commutators should, 
however, be avoided. While the machine is running the brushes 
should not be lifted off, since the large sparks thereby produced 
strongly attack the brushes and the commutator, and this favorite 
amusement of the workmen should be strictly forbidden. 

When the machine is for the first time set in motion, the com- 
mutator should be gone over with a smooth file or emery paper 
to remove any projections of the insulation between the metallic 
plates, which readily swell when the machine stands in a damp 
place. The commutator should also daily be freed, by wiping, 
from copper-dust, and if after some time it wears unevenly be 
made smooth with a file. 

The inductor-ring should at least once every week be cleaned 
from copper-dust by means of a small bellows or other instrument. 
Movable articles of iron and steel should be kept away from the 
machine when running, as they might be attracted by the portions 
of the machine which have become strongly magnetic. 

The object- and anode-wires must be insulated from each other, 




ELECTRO-PLATING ESTABLISHMENTS. 95 

as well as from the ground and damp brick-work by dry wood 
or porcelain, and the places of junction kept bright. 

The employment of special wire-carriers, of the form shown in 
Fig 57, is advisable. They consist of cast-iron arms, provided 
on the ends with a case, between the lower 
and upper cover of which are disks of hard F 'g- 57. 

rubber. 

To regulate the current resistance boards 
or current-regulators are used. They are 
constructed according to the same principles 
as those described under "Arrangement with 
Elements" (p .76), only the spirals are longer 
and of a larger cross-section, and the entire 
instrument is stronger. Instead of upon wood, the contact 
buttons are mounted upon slate plates, as wood would be carbon- 
ized by the spirals becoming hot. 

In case one machine has to feed several baths of dissimilar 
nature and composition, the regulation of the current for all the 
baths in the main conducting wire is not feasible on account of 
the different resistances ; and it will be necessary to place a resist- 
ance board in front of every bath. With dynamos of the Schuc- 
kert and Lahmeyer type, which are very practical, it will be 
further necessary to place a resistance board (the resistance board 
of the dynamo) in the windings of the machine, in order to be 
enabled to generate more or less current, as may be required, and 
to avoid an unnecessary consumption of power. From the scheme 
Fig. 58, for such a machine, with its auxiliary apparatus, the 
main conducting wire and a few baths, the reader will readily see 
what is required. 

The dynamo resistance board will have to be placed so that the 
machine yields somewhat more current than with due considera- 
tion to the object-area is required for all the baths, while the 
supply of current for each bath is regulated by the resistance 
board placed in front of it. In the scheme Fig. 58 are sketched 
two further instruments for measuring the quantity and the 
electro-motive force of the current ; by the first, called the 
amperemeter, or better ammeter, the whole current-strength can be 
directly read off in amperes ; and by the other, called the volt- 



96 



ELECTRO-DEPOSITION OF METALS. 




meter, the electro-motive force or tension in volts. The ampere- 
meter is placed in one conducting wire only, either in that of the 
object or of the anodes, while the voltmeter is connected with 



ELECTRO-PLATING ESTABLISHMENTS. 



97 



both, one setting-screw being joined, on the points where the ten- 
sion is to be measured, to the object-wire by a 0.039-inch thick 
copper wire, and the other to the anode wire. In the sketch 
(Fig. 58), the voltmeter being directly in contact with the poles 
of the machine will indicate the tension produced by it. This 
mode of placing the measuring instruments is, however, not suit- 

Fisr. 59. 




able for establishments using baths of different compositions and 
different resistances ; in such case the tension must be measured 

7 



98 



ELECTRO-DEPOSITION OF METALS. 



on the bath itself, and consequently the voltmeter has to be placed 
in the conducting wire between the resistance board of each bath 
and the bath itself. However, for a large establishment, using 
many baths, it would be quite an item of expense to provide each 
bath with a special voltmeter. But this is not necessary, one 
voltmeter sufficing for three, four, or even more baths. In order 
conveniently to read off on the voltmeter the tension of the 
current passing into one of these baths a shunt is required, the 
construction of which is seen from Figs. 59 and 60. 

Fig. 59 shows the coupling of the main object-wire ( — ) ana 
the main anode-wire ( + ), with the resistance boards R x and R 2 , 
the voltmeter V, the shunt U, and the two baths. 

In Fig. 60 the coupling is enlarged, and upon this the fol- 
lowing description is based : Suppose the main object-wire and 
anode- wire to be connected with the corresponding poles of a 

Fiji. 60. 




dynamo-machine or a battery, which for the sake of a clearer 
view is omitted in the illustration. The shunt XI consists of a 
brass handle, mounted with a brass foot, upon a board ; in the 
foot is a screw, with which is connected by a 0.039-inch thick 
copper-wire one of the pole-screws of the voltmeter. The brass 
handle drags with spring pressure upon contact buttons connected 



ELECTRO-PLATING ESTABLISHMENTS. 99 

by copper wire with the setting screws 1, 2, 3, 4, 5 (upon the 
shunt board), which serve for the reception of the 0.039-inch 
thick insulated wires 1, 2, 3, 4, for measuring the tension, which 
branch off from the various baths or resistance boards. The 
other pole-screw of the voltmeter is directly connected with the 
main anode-wire. From the main object-wire, a wire, whose cross- 
section depends on the strength of the working current, passes 
to the screw marked " strong" of the resistance board R x ; the 
screw marked " weak" of the resistance board R x is connected 
by a correspondingly stout wire with the object-wire of bath I, 
and at the same time with the binding-screw 1 of the shunt. 
The resistance board R 2 , of the bath II, is in the same manner 
connected with the main object-wire, the bath, and the binding- 
screw 2 of the shunt ; also the resistance boards R 3 and R A of the 
baths III and IV, which are not shown in the illustration. With 
the main anode-wire each bath is directly connected by leading 
the current to an anode-rod of the bath by means of binding- 
screws and a stout copper wire, and establishing a metallic con- 
nection between this anode-rod and the next one. However, in- 
stead of connecting both, the current may also be led from the 
main anode-wire to each anode-rod. 

In the illustration, the handle of the shunt rests upon the 
second contact-button to the left, which is connected with the 
binding-screw 2 of the board. In the latter is secured the wire 
for measuring the tension of the resistance board R 2 ; and hence 
the voltmeter Fwill indicate the tension of the current in bath II. 
Suppose bath II is full of objects, and with the position of the 
handle of the resistance board at " weak," as shown in the illus- 
tration, the voltmeter indicates 1.5 volts, while the most suitable 
tension for the bath is 2.5 volts, the handle of the resistance board 
is turned to the left until the needle of the voltmeter indicates the 
desired 2.5 volts. 

By turning the handle of the shunt Z7to the left, so that it 
rests upon the contact-button 1, the measuring wire of bath II is 
thrown out, and the voltmeter indicates the tension in bath I. If 
the handle rests upon contact-button 3, the tension in bath III is 
indicated, and so on. 

In working the different baths in a larger establishment, each 



100 



ELECTRO-DEPOSITION OF METALS. 



bath is best directly fed from the main conducting wire after the 
current has been brought to the proper strength by the resistance 
board. Coupling the baths one after another so that the current 



Fie. 61. 



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ELECTRO-PLATING ESTABLISHMENTS. 101 

passes from one bath to the other is only practicable for metal- 
lurgical processes — gaining of metals — where every bath contains 
the same area of objects and anodes, has the same resistance, and 
works under the same conditions. 

Fig. 61 shows the ground plan of an electro-plating establish- 
ment. NN 1 is a dyuamo-electric machine, with 300 amperes at 
4 volts' tension. The resistance board belonging to the machine, 
which is placed in the conductor, is indicated by No. l,and is 
screwed to the wall. The main conductors, marked — and -f , run 
along the wall, from which they are separated by wood, and consist 
of rods of pure copper 0.59 inch in diameter. The rods are con- 
nected with each other by brass coupling-boxes with screws. 
From the negative pole and the positive pole of the machine to 
the object-wire and anode-wire lead two wires, each 0.27 inch in 
diameter ; one end of each is bent to a flat loop and secured under 
the pole screws of the machine, while the other ends are screwed 
into the second bore of the binding-screws screwed upon each con- 
ductor. To the right and left of the machine the baths are placed ; 
2k, indicating zinc bath ; Ni Ni, nickel baths ; Ku, copper cyan- 
ide bath ; Mg, brass bath ; S K, acid copper bath ; Si, silver bath ; 
and Go, gold bath. Each of the first-named five baths has its 
own resistance board designated by 2, 3, 4, 5, 6. However, be- 
fore reaching the acid copper bath, and the silver and gold baths, 
the current is conducted through two resistance boards, 7 and 8. 
Since these baths require a current of only slight electro-motive 
force, it is necessary to place two, and in many cases even three 
or four, resistance boards, one after another, unless it be preferred 
to feed these baths with a special machine of less tension. 

From Fig. 61 it will be seen that the current weakened by the 
resistance boards 7 and 8 serves for conjointly feeding the acid- 
copper, silver, and gold baths. Hence, practically, only one bath 
can be allowed to work at one time, as otherwise each bath would 
have to be provided with as many resistance boards as would be 
required for the reduction of the tension. For want of space the 
gold bath is placed in the sketch behind the silver bath ; but 
as their resistance is not the same, they must also be placed 
parallel. 



102 



ELECTRO-DEPOSITION OF METALS. 



The coupling of the voltmeter and shunt is omitted in the il- 
lustration. Their arrangement will be understood from Fig. 59. 

L is the lye-kettle ; it serves for cleansing the objects by means 
of hot caustic potash or soda-lye from grinding and polishing dirt 
and oil. Instead of the preparatory cleansing with hot lye, which 
saponifies the oils, the objects may be brushed off with benzine, 
oil of turpentine, or petroleum, the principal thing being the re- 
moval of the greater portion of the grease and dirt, so that the final 
cleansing, which is effected with lime paste, may not require too 
much time and labor. It is also advisable to cleanse the objects, 
in one way or the other, immediately after grinding, as the dirt, 
which forms a sort of solid crust with the oil, is difficult to soften 
and to remove when once hard. The table for freeing the articles 
from grease stands alongside the lye-kettle, and is shown in per- 
spective in Fig. 62. It consists of a box with legs, which is 
divided by four partitions into two large divisions, A and B, and 
three smaller ones, C, D, and E. The separate divisions are lined 




with sheet lead. Across divisions A and B boards covered 
with cloth are laid, upon which the articles are brushed for the 
final cleansing with lime paste. Over each of these divisions is a 
rose-jet, provided with a cock, under which the articles are rinsed 
with water. The discharge pipes from A and B are provided 
with valves, and are tightly soldered into the bottom of the box. 
Of the smaller partitions, T> serves for the reception of the lime 



ELECTRO-PLATING ESTABLISHMENTS. 103 

paste, while C and E each contain two pots or small stoneware 
vats with pickling fluid. In Fig. 61 these vats are indicated by 
11 and 12. The two marked 11 contain dilute sulphuric acid for 
pickling iron and steel articles, while those marked 12 contain 
dilute potassium cyanide solution for pickling copper and its 
alloys, and Britannia, etc. For cleansing smaller articles, four 
men can atone time work on such a table; but for cleansing larger 
articles only two. The advantages of such a box-table are that 
everything is handy together; that the pickle, in case a pot 
should break, cannot run over the floor of the workshop ; and that 
the latter is not spoiled by pickle dropping from the objects. The 
small box K, on the side of the table, serves for the reception of 
the various scratch-brushes. 

Between the lye-kettle L and the box-table in Fig. 61 is a frame, 
14, for the reception of brass and copper wire hooks of various 
sizes and shapes suitable for suspending the objects in the bath. 

The reservoir W, filled with water, standing in front of the 
machine, serves for the reception of the cleansed and pickled ob- 
jects, if for some reason or another they cannot be immediately 
brought into the bath. 

H W is the hot water reservoir in which the plated objects are 
heated to the temperature of the hot water, so that they may 
quickly dry in the subsequent rubbing in the sawdust box Sp. 
Before polishing the deposits, iron and steel objects are thoroughly 
dried in the drying chamber T (Fig. 61), heated either by steam 
or direct fire. By finally adding to the appliances a large table, 
13, for sorting and tying the objects on the copper wires, and a 
few shelves not shown in the illustration, everything necessary 
for operating without disturbance will have been provided. 

What has been said in the preceding section in regard to the 
conducting wires, vats, conducting rods, anodes, etc., also applies 
to establishments using electro-dynamo machines. 

In calculating the thickness of the conducting wires for dyna- 
mos, 1 square millimetre (0.001 square inch) of conducting cross- 
section is to be allowed for every 3 amperes for so-called short 
circuits up to 20 metres (21.87 yards). This is valid for currents 
up to 500 amperes ; for longer circuits 1 \ to 2 amperes are calcu- 
lated for the square millimetre of conducting cross-section. 



104 ELECTRO-DEPOSITION OF METALS. 



CHAPTER Y. 

TREATMENT OF METALLIC ARTICLES. 

The objects having to undergo both a mechanical and chemical 
preparation, each of them will be considered separately. 

A. Mechanical Treatment. 

1. Before electro-plating. — If the objects are not to be electro- 
plated while in a crude state, which is but rarely feasible, the 
mechanical treatment consists in imparting to them a cleaner sur- 
face by scratch-brushing, or a smoother and more lustrous one by 
grinding and polishing. It may here be explicitly stated that 
scratch-brushing of electro-plated objects is not to be considered 
a part of their preparation, since such scratch-brushing is executed 
in the midst of or after the electro-plating process, its object being 
to effect a change of the electro-deposition in more than one 
direction, and not the cleansing of the surface of the metallic 
base. The following directions, therefore, apply only to the 
scratch-brushing of objects not electro-plated. The scratch-brush- 
ing of electro-depositions will be considered later on. In regard 
to grinding, we have to deal with the subject only in so far as it 
relates to smoothing rough surfaces by the use of grinding pow- 
ders possessing greater hardness than the metal to be ground ; 
with grinding in the sense of instrument-grinding, the primary 
object of which is to provide the instrument with a cutting edge, 
we have nothing to do. 

Scratch-brushing may be effected either by hand or by a scratch - 
brush lathe. In the first place scratch-brushes of more or less 
hard brass or steel wire, according to the hardness of the metal to 
be manipulated, are used. Various forms of brushes are employed, 
the most common ones being shown in the accompanying illustra- 
tions (Figs. 63 to 71). 



TREATMENT OF METALLIC ARTICLES. 



105 



Fig. 70 shows swing brushes for frosting or satin finish, with 
four knots of medium brass or steel wire, and Fig. 71 the plater's 
lathe goblet scratch-brush. 

In scratch-brushing it is recommended to remove, or at least to 
soften, the uppermost hard and dirty crust (the scale) by immers- 
ing the objects in a pickle, the nature of which depends on the 



Fig. 63. 



Fig. 64. 



Fig. 65. 



Fig. 66. 





Fig. 67. 



Fig. 68. 



Fig. 69. 





variety of metal, so that a complete removal of all im- 
purities and non-metallic substances may be effected by 
means of the scratch-brush in conjunction with sand, 
pumice-stone, powder, or emery. The work is com- 
plete only when the article shows a clean metallic sur- 
face, otherwise the brushing (scouring) must be con- 



106 



ELECTRO-DEPOSITION OF METALS. 



tinned. Scratch-brushes must be carefully handled and looked 
after, and their wires kept in good order. When they become 
bent they have to be straightened, which is most readily effected 
by several times drawing the brush, held in a slanting position, 
over a sharp grater such as is used in the kitchen. By this 
means the wires become disentangled and straightened out. 



Fig. 70. 



Fig. 71. 





Hand scratch-brushing being slow and tedious work, large 
establishments use circular scratch-brushes which are attached to 
the spindle of a lathe. These circular brushes consist of round 
wooden cases in which, according to requirement, 1 to 6 or more 
rows of wire bundles (see Fig. 72) are inserted. 

Fig. 72. 




Brushes with wooden cases are, however, more suitable for 
scratch -brushing deposits than for cleansing the metallic base, 
since for the latter purpose a more energetic pressure is usually 
applied, in consequence of which the bundles bend and even 
break off, if the wire is anywise brittle. For cleansing purposes 
a circular scratch-brush, which the workman can readily refurnish 



TREATMENT OF METALLIC ARTICLES. 107 

with new bundles of wire, deserves the preference. It is con- 
structed as follows: A round iron diskaboutO.il inch thick, 
and from 5f to 7f inches in diameter, is provided in the centre 
with a hole so that it can be conveniently placed upon the spindle 
of the lathe. At a distance of from 0.19 to 0.31 inch from the 
periphery of the disk holes 0.079 to 0.11 inch in diameter are 
drilled, so that between each two holes is a distance of 0.15 inch. 
Draw through these holes bundles of wire about f3.93 inches long, 
so that they project an equal distance on both sides. Then bend 
the bundles towards the periphery, and on each side of the iron 
disk place a wooden disk 0.31 to 0.39 inch thick. The periphery 
of the wooden disk, on the side next to the iron disk, should be 
turned semi-annular, so that the wooden disks when secured to 
the spindle press very lightly upon the wire bundles, and the 
latter remain very mobile. When a circular scratch-brush con- 
structed in this manner and secured to the lathe is allowed to 
make from 1 800 to 2000 revolutions per minute, the bundles of 
wire, in consequence of the centrifugal force, stand very rigid, but 
being mobile will give way under too strong a pressure without 
breaking off, and can thus be utilized to the utmost. When re- 
quired, the iron disk can be refurnished with wires in less than 
half an hour. An error frequently committed is that the objects 
to be cleansed are pressed with too heavy a pressure against the 
wire brushes. This is useless, since only the sharp points of the 
wire are effective, the lateral surfaces of the bundles removing 
next to nothing from the articles. 

Brushes. — A definition of these instruments is unnecessary, and 
we shall simply indicate the various kinds suitable to the different 
operations. 

The fire-gilder employs, for equallizing the coating of amalgam, 
a long-handled brush, the bristles of which are long and very 
stiff. The electro-gilder uses a brush (Fig. 73) with long and 
flexible bristles. 

For scouring with sand and pumice-stone alloys containing 
nickel, such as German silver, which are difficult to cleanse in 
acids, the preceding brush, with smaller and stiffer bristles, 

used. 



108 ELECTRO-DEPOSITION OF METALS. 

The gilder of watch-works has an oval brush (Fig. 74), with 
stiff and short bristles for graining the silver. 

The galvanoplastic operator, for coating moulds with black- 
lead, besides a number of pencils, uses also three kinds of brushes 
— the watchmaker's (Fig. 75), a hat-brush, and a blacking-brush. 
The bronzer uses all kinds of brushes. 

Fig. 73. Fig. 74. Fig. 75. 




Brushes are perfectly freed from adherent grease by washing 
with benzine or bisulphide of carbon. 

In large establishments engaged in electro-plating cast-iron 
without previous grinding, the use of the sand-blast in place of 
the circular wire brush has recently been introduced with great 
advantage. Objects with deep depressions, which cannot be 
reached with the scratch-brush, as well as small objects, which 
cannot be conveniently held in the hand and pressed against 
the revolving scratch-brush, can be brought by the sand-blast 
into a state of sufficient metallic purity for the electro-plating 
process. However, while the revolving scratch-brushes impart 
to the objects a certain lustre, they acquire by the sand-blast a 
dead lustre, and, hence, the blast is also frequently used for the 
purpose of deadening lustrous surfaces to their entire extent, or 
of producing contrasts — for instance, dead designs upon a lus- 
trous ground, or vice versa. 

Fig. 76 shows such a sand-blast. The compressed air, whose 
pressure must be at least equal to an 18J-inch column of water, 
passes through the blast-pipe A into a nozzle running horizontally 
through the machine, and carries away from there a jet of sand, 
which falls into the outflowing blast and is hurled upon the 
objects placed under the nozzle. The objects rest upon sheet- 
iron plates or in boxes of sheet-iron, which, moving at a slow 
rate, pass under the nozzle ; the motion is effected by the shafts 
B B, with the use of belts. To prevent dust, the machine is 
encased in a wooden or sheet-iron case, a few windows allowing 



TREATMENT OF METALLIC ARTICLES. 



109 



a view of the interior. The sand used in blasting collects in a 
box, and is returned to the sand-reservoir by an elevator. 

The jet of sand acts not only upon the upper side of the 
objects, which it strikes first, but also almost as energetically 
upon the lower, so that, as a rule, the cleansing process is com- 



Fie. 76. 




pleted by one operation. Objects of a specially unfavorable shape 
must be passed twice or three times under the nozzle. 

If a clean metallic surface is to be given at one time to a large 
number of small articles, such as buckles, steel beads, metal 
buttons, steel watch-chains, ferrules, etc., a tumbling drum or box 
is frequently used. It generally consists of a cylindrical or 
polygonal box having a side door for the introduction of the 
work, together with sharp sand or emery, and is mounted hori- 



110 



ELECTEO-DEPOSITION OF METALS. 



zontally on an axis furnished with a winch or pulley, so as to be 
revolved either by hand or power, as may be desired. In order 
to prevent certain objects, like hooks for ladies' dresses and the 
like, from catching each other and accumulating into a mass, a 
number of nails or wooden pegs are fixed in the interior of the 
drum. 

A very practical form of tumbling drum, in which a change 
of position of the contents must constantly take place, is shown in 
Fig. 77. The drum A, of wood or iron, is obliquely placed upon 
the shaft B. The objects are introduced through the door C. 
The drum is revolved by a crank, or by a belt by means of the 

Fie. 77. 




pulley D. All portions of the drum describe thereby ellipses, the 
Malls of the drum being now raised (indicated by the dotted lines) 
and then lowered, so that the objects in the drum are in constant 
motion and rub against each other. By introducing together 
with the objects a suitable polishing powder with oil or water, 
such drums may be used not only for the preparatory cleansing 
of the objects, but also for polishing. 

For ordinary polishing the articles are brought into the tumbling 
drum, together with small pieces of leather waste (leather shav- 
ings), and taken out in one or two days. However, to produce 
an actually good polish a somewhat more complicated method has 
to be pursued. The articles are first freed from adhering oxide 
by washing in water containing 5 per cent, of sulphuric acid, 
rinsed, and dried in a drying chamber or in a pan over a fire. 
They are next brought into the tumbling drum together with 
sharp sand, such as is used in glass-making, and revolved for 



TREATMENT OF METALLIC ARTICLES. Ill 

about 12 hours, when they are taken from the drum and freed 
from the admixed sand by sifting. They are then returned to 
the drum, together with soft, fibrous sawdust, to free them from 
adhering sand, and at the same time to give them a smoother 
surface. They are now again taken from the drum, freed from 
sawdust and returned to the drum, together with leather shav- 
ings. They now remain in the drum until they have acquired 
the desired polish, which, according to the size and shape of the 
articles and the degree of polish required, may frequently take 
two weeks or more. Articles of different shapes and sizes are 
best treated together, time being thereby saved. The process is 
also accelerated by adding some fat oil to the leather shavings, 
which, of course, must be omitted when, after long use, the 
shavings have become quite greasy. The drum should be filled 
about half full, otherwise the articles do not roll freely and 
polishing is retarded. On the other hand, when the drum is less 
than half full there is danger of the articles bending, or in case 
they are hardened, for instance buckles, of breaking. 

For many purposes polishing in the tumbling drum is of great 
advantage, since, independent of its cheapness, the sharp edges of 
the articles are at the same time rounded off. However, with 
articles the edges of which have to remain sharp, the process 
cannot be employed. 

The tumbling drum in which the articles are treated with sand 
cannot be used for polishing with leather shavings, it being next 
to impossible to free it entirely from sand. The drums should 
make from 50 to 70 revolutions per minute ; if allowed to revolve 
more rapidly, the articles take part in the revolutions without 
rolling together, which, of course, would prevent polishing. 

The brightening of articles of iron and steel may be simplified 
by using water to which 1 per cent, of sulphuric acid has been 
added. The drum used for the purpose must, of course, be 
water-tight. By the addition of sand the process is accelerated. 
Nickel and copper blanks for coins are also cleansed in this man- 
ner. They are brought into the tumbling drum, together with a 
pickling- fluid and, when sufficiently treated, are taken out, rinsed, 
dried in sawdust, and finally stamped. 




112 ELECTRO-DEPOSITION OF METALS. 

Grinding. — For grinding the objects for the electro-plating 
process, wooden disks covered with leather coated with emery of 
various degrees of fineness are almost ex- 
Fig. 78. clusively used. The wooden disks are 
made of thoroughly seasoned poplar in the 
manner shown in Fig. 78. The separate 
pieces are radially glued together, and upon 
each side in the centre a strengthening 
piece is glued and secured with screws so 
that each segment of the wooden disk is 
connected with the strengthening piece. 
The centre of the disk is then provided 
with a hole corresponding to the diameter of the spindle of the 
grinding lathe, to which it is secured by means of wedges. The 
periphery as well as the sides are then turned smooth. A good 
quality of leather previously soaked in water and cut into strips 
corresponding to the width of the wooden disk is then glued to 
the periphery of the disk, and still further secured by pins of soft 
wood. When the glue is dry the disk is again wedged upon the 
spindle and the leather carefully turned; it is then ready for 
coating with emery. 

For this purpose three different kinds of emery are used, a 
coarse quality (Nos. 60 to 80) for preparatory grinding, a finer 
quality (No. 00) for fine grinding, and the finest quality (No. 0000) 
for imparting lustre. The disks thus coated are termed respec- 
tively " roughing wheel," " medium wheel," and " fine wheel." 
With the first the surfaces of the objects are freed from the rough 
crust. The coarse-grained emery used for this purpose, however, 
leaves scratches, which have to be removed by grinding upon the 
medium wheel until the surface of the objects shows only the 
marks due to the finer quality of emery, which are in their turn 
removed by the fine wheel. 

In most cases brushing; with a circular bristle brush mav be 
substituted for the last grinding, the articles being moistened with 
a mixture of oil and emery No. 0000. Care must be had not to 
execute the brushing, nor the grinding with the finer quality of 
emery, in the same direction as the preceding grinding, but in a 
direction at a right angle to it. 



TREATMENT OF METALLIC ARTICLES. 113 

Treatment of the grinding disks. — The coating of the roughing 
wheels with emery is effected by applying to them a good quality 
of glue and rolling them in the dry coarse emery powder. For 
the medium and fine wheels, however, the emery is mixed with 
the glue and the mixture applied to the leather. When the first 
coat is dry, a second is applied, and finally a third. The whole 
is then thoroughly dried in a warm place. Before use, a piece of 
tallow is held to the revolving disk for the purpose of imparting 
a certain greasiness to it, and in order to remove any roughness 
due to an unequal application of the emery it is smoothed by 
pressing a smooth stone against it. While the preparatory grind- 
ing upon the roughing wheel is executed dry, i. e., without the use 
of oil or fat, in fine grinding the objects are frequently moistened 
with a mixture of oil or tallow and the corresponding No. of 
emery. When the layer of emery is used up, the remainder is 
soaked with warm water and scraped off with a dull knife. The 
leather of the disks on which oil or tallow has been used is then 
thoroughly rubbed with caustic lime or Vienna lime* to remove 
the greasiness, which would prevent the adherence of the layer of 
glue and emery to be applied later on. When the leather is 
thoroughly dry a fresh layer of emery may at once be applied. 

Grinding lathes. — For use, the grinding disks or buffs are 
wedged upon a conical cast-steel spindle provided with a pulley 
and working in hard-wood bearings, as plainly shown in Fig. 79. 
The cast-iron standards are screwed to the floor ; the wooden bear- 
ings can be shifted forward and backward by wedges and secured 
in a determined position by a set screw, thus facilitating the 
removal of the spindle after throwing off the belt. The disks 
being wedged upon a conical spindle they always run centrically. 
The changing of the disks requires but a few seconds, and on ac- 
count of the slight friction of the points of the spindle in the 
wooden bearings the consumption of power is very slight. 

To avoid the necessity of throwing off the belt while changing 
the grinding disks, double machines (Fig. 80) are used, the prin- 

* Vienna lime is prepared from a variety of dolomite which is first burned, 
then slacked, and finally glowed for a few hours. It consists of lime and mag- 
nesia, and should be kept in well-closed cans, as otherwise it absorbs carbonic 
acid and moisture from the air, and becomes useless. 



114 



ELECTEO-DEPOSITION OF METALS. 



ciple of conical spindles being, however, preserved. The shaft is 
provided with loose and fast pulley and coupling lever. 



Fig. 79. 




Grinding is executed by pressing the surfaces to be ground 
against the face of the disk, moving the objects constantly to and 



Fig. 80. 




fro. The operation requires a certain manual skill, since, without 
good reason, no more should be ground away on one place than 
on another. Special care and skill are required for grinding 
large round surfaces. 



TREATMENT OF METALLIC ARTICLES. 



115 



If the objects are not to be treated with the fine wheel, fine 
grinding is succeeded by brushing with oil and emery by means 
of circular brushes formed of bristles set in disks of wood (see 
Fig. 85). Genuine bristles being at present very expensive, 
vegetable fibre, so-called fibres, has been successfully substituted 
for them, the wooden disk being replaced by an iron case, in the 
bell-shaped cheeks of which the fibre-bundles are secured by 
means of strong nuts. Before use it is advisable to saturate the 
fibre-bundles with oil in order to deprive them of their brittleness, 
and thus improve their lasting quality. 

The grinding lathe (Fig. 81) is provided with such a fibre- 
brush ; it can, of course, be just as well placed upon the conical 




spindles of double machines. The iron case is provided with a 
conical hole corresponding exactly to the conical spindle, the 
large frictional surface preventing the turning of the brush upon 
the spindle or its running off. 

In regard to grinding the various metals, the procedure, 
according to the hardness of the metal, is as follows : — 

Iron and steel articles are first ground upon the roughing 
wheel, then fine-ground upon the medium wheel, and finally 
upon the fine wheel, or brushed with emery with the circular 
brush. Very rough iron surfaces may first be ground upon solid 
emery wheels before being worked upon the roughing wheel. 



116 



ELECTKO-DEPOSITION OF METALS. 



For depressed surfaces which cannot be reached with the large 
emery disks, small disks of walrus-hide coated with glue and 
emery are placed upon the point of the spindle of the polishing 
lathe (see Fig. 85). 

Brass and copper castings are first ground upon roughing 
wheels, which have lost part of their sharpness and will no longer 
attack iron ; they are then ground fine upon the medium wheel, 
and finally polished upon cloth or felt disks (bobs). (See below, 
under Polishing.) 

Sheets of brass, German silver, and copper, as furnished by 
rolling-mills, are only brushed with emery and then polished 
with Vienna lime or rouge upon bobs. 

Zinc castings, as, for instance, those produced in lamp factories, 
are first thoroughly brushed by means of circular brushes and 
emery, and then polished upon cloth bobs. 

Sheet zinc is only polished with Vienna lime and oil upon cloth 
bobs secured to the spindle shown in Fig. 86. 

Polishing. — As will be seen from the foregoing, polishing 
serves for making the articles ready, i. e., the final lustre is im- 
parted to them upon soft polishing disks with the use of fine 
polishing powders. The polishing disks or bobs of fine felt, 
shirting, or cloth, are secured to the polishing lathe, and, accord- 
ing to the hardness of the metal to be polished, make 2000 to 

2500 revolutions per minute. A foot- 
lathe, such as is shown in Fig. 82, 
makes generally not over 1800 revo- 
lutions per minute. Cloth bobs are 
made by placing pieces of cloth one 
upon another in the manner described 
under "Nickelling of sheet zinc," cut- 
ting out the centre corresponding to 
the diameter of the spindle, and secur- 
ing the disks of cloth by means of nuts 
bet wen two wooden cheeks upon the 
spindle of the polishing lathe. In 
place of cloth bobs, solid round disks 
of felt or wooden disks covered with 
a layer of felt may be used, especially 
for polishing smooth objects without 



Fig. 82. 




TREATMENT OF METALLIC ARTICLES. 



117 



Fig. 83. 



depressions, the fineness and softness of the felt depending on the 
degree of polish to be imparted and the hardness of the metal to 
be manipulated. 

The foot-lathe shown in Fig. 83 is designed for light grinding, 
polishing, and buffing, and is especially suited for polishing silver- 
plate and silver. It is constructed of iron and steel, and made 
very rigid and strong to prevent vibration. It stands 3 feet 9 
inches from floor to centre of spindle, has a 26-inch driving-wheel 
turned with grooves for three dif- 
ferent speeds, and will run the 
spindle easily at from 300 to 3000 
revolutions per mi n ute. The spin- 
dle as shown in the illustration is 
suitable for leather, muslin, and 
swan's-down bobs, buffs, and mops. 
This can be unscrewed and re- 
placed by another spindle, which 
is furnished with a taper screw 
for the bosses of circular brushes. 

Double polishing lathes, accord- 
ing to the American patterns 
(Figs. 84 and 85), are used for 
polishing objects of not too large 
dimensions, while the lathe shown 
in Fig. 86 serves chiefly for polish- 
ing large sheets, the latter being 
placed upon a smooth wooden sup- 
port which rests upon the knees of 
the workman, as will be described 
later on in speaking of the nickel- 
ling of sheet zinc. 

Fig. 85 shows a double polish- 
ing lathe of larger size ; it carries 

on one side a large felt disk and a small brush, and upon the 
other a circular brush and a small walrus-hide buff. The spindle 
of the small polishing lathe, Fig. 84, carries a cloth bob. 

The lathe (Fig. 87) is manufactured by the Hanson & Van 
Winkle Co., of Newark, N". J. It is shown on a cast-iron pedestal, 




118 



ELECTRO-DEPOSITION OF METALS. 



from which it can be disconnected and placed on a bench, if re- 
quired. It is made to run at a speed of 3000 revolutions per 



Fie. 84. 




Fig. 85. 




Fig. 86. 




minute, at which speed the most satisfactory results are obtained 
with muslin buffs, etc. 



TREATMENT OF METALLIC ARTICLES. 



119 



The lathe is made with steel spindles, hard-metal bearings, and 
is designed for quick speeds. By reason of the distribution of 



Fie. 87. 




metal it runs without vibrations. It stands 10 inches high to 
centre, has spindle 3 feet long, 1 \ inches diameter, with collars on 
both ends of spindle. The pulley is 4 inches in diameter, 3J 
inches face. The spindle is 1 inch diameter between collars. 
The lathe is furnished with fast and loose pulleys where re- 
quired. Detachable taper ends are shown, on which the smallest 
brush can be run. 

The belt strapping attachment shown in Fig. 88, which is also 
manufactured by the Hanson & Van Winkle Co., of Newark, N. J., 
can be applied to the above-described or other size polishing lathe 
that will carry a 12-inch wheel. Flanged wheels are supplied to 
readily take the place of the polishing wheel, and a canvas and 
rubber endless belt from 1 to 2 J inches wide and 12 feet total 
length is used, to which the different grades of emery or other 
material are applied. 

These machines, of which several styles are made, are largely 



120 ELECTRO-DEPOSITION OF METALS. 

used by manufacturers of saddlery and carriage hardware, and 
on regularly shaped articles that cannot be conveniently polished 
on a circular wheel. 

Fiff. ££• 




Self-acting polishing lathes for sheet-metal will be discussed 
under " Nickelling of zinc sheet." 

According to the hardness of the material to be polished, ferric 
oxide (colcothar or rouge), tripoli, Vienna lime, etc., in the state 
of an impalpable powder, and generally mixed with oil, or some- 
times with alcohol, are used as polishing agents. For hard metals 
an impalpable rouge of great hardness (No. F of commerce) is 
employed, for softer metals a softer rouge (No. F F F) or Vienna 
lime, tripoli, etc. 

It is of advantage to melt the rouge with melted wax and a 
small quantity of tallow, and cast the mixture in moulds with the 
aid of strong pressure. The sticks thus formed are sufficiently 
greasy to render the use of oil superfluous. In order to impreg- 
nate the surface of the polishing bob with the polishing material, 



TREATMENT OF METALLIC ARTICLES. 121 

hold one of the sticks for a second against the revolving disk, 
and then polish the objects by pressing them against the disk, 
diligently moving them to and fro. The polishing bob must not 
be too heavily impregnated with rouge, since a surplus of the 
latter smears instead of cutting well. In polishing with Vienna 
lime, it, is advisable to moisten the objects to be polished, with oil, 
while the polishing bobs are saturated with the lime by holding a 
piece of it against them. 

Another process of polishing, called burnishing, is executed 
by means of tools usually made of steel for the first or grounding 
process, or of a very hard stone, such as agate or blood-stone, for 
finishing. Burnishing is applied to the final polishing of depo- 
sitions of the noble metals. 

2. Mechanical treatment during and after the electro-plating 
process. — In this connection, scratch-brushing the depositions will 
be first considered, the object of this operation being, on the one 
hand, to promote the regular formation of certain deposits ; on the 
other, to effect a change in the physical properties of the deposits ; 
and, finally, to ascertain whether the deposit adheres to the basis- 
metal. 

If it is seen by the irregular formation of the deposit that the 
basis-metal has not been cleaned with sufficient care by the pre- 
paratory scratch-brushing, the object has to be taken from the 
bath and the defective places again scratch-brushed with the 
application of water and sand, or pumice-stone, when the object 
is again pickled and replaced in the bath. 

On the other hand, electro-deposited metals are always more or 
less porous, they having, so to say, a net-like structure, though it 
may not be visible to the naked eye. By scratch-brushing the 
meshes of the net are made closer by particles of metals being 
forced into them by the brush, and the deposit is thus rendered 
capable of receiving additional layers of metal. Furthermore, 
by scratch-brushing the dead deposits acquire a certain lustre 
which is enhanced by the subsequent polishing process. Finally, 
by an unsparing application of the scratch-brush, it will best be 
seen whether the union of the deposit with the basis-metal is 
sufficiently intimate to stand the subsequent mechanical treatment 
in polishing without becoming detached. 



122 ELECTEO-DEPOSITION OF METALS. 

According to the object in view, and the hardness of the de- 
posit to be manipulated, scratch-brushes of steel or brass wire are 
chosen. For nickel, which, as a rule, requires scratch-brushing 
least, and chiefly only for the production of very thick deposits, 
steel wire of 0.2 millimetre thickness is taken; for deposits of 
copper, brass, and zinc, brass wire of 0.2 millimetre ; for silver, 
brass wire of 0.15 millimetre; and for gold, brass wire of 0.07 to 
0.1 millimetre. Scratch-brushing is seldom done dry ; the tool 
as well as the pieces should be constantly kept wet with liquids, 
especially such as produce a lather in brushing, for instance, 
water and vinegar, or sour wine, or solutions of cream of tartar 
or alum, when it is desired to brighten a gold deposit which is 
too dark ; but that most generally used is a decoction of licorice- 
root, of horse-chestnut, of marshmallow, of soapwort, or of the 
bark of Panama-wood, all of which, being slightly mucilaginous, 
allow of a gentle scouring with the scratch-brush, with the pro- 
duction of an abundant lather. A good adjunct for scratch- 
brushing is a shallow wooden tub containing the liquid employed, 
with a board laid across it nearly level with the edges, which, 
however, project a little above. This board serves as a rest for 
the pieces. 

The hand scratch-brush, when operating upon small objects, is 
held by the workman in the same manner as a paint brush, and 
is moved over the object with a back and forward motion im- 
parted by the wrist only, the forearm resting on the edge of the 
tub. For larger objects, the workman holds his extended fingers 
close to the lower part of the scratch-brush, so as to give the wires 
a certain support, and, with raised elbow, strikes the pieces re- 
peatedly, at the same time giving the tool a sliding motion. When 
a hollow is met with, which cannot be scoured longitudinally, a 
twisting motion is imparted to the tool. 

The lathe brush (Fig. 89) is mounted upon a spindle, and is 
provided above with a small reservoir to contain the lubricating 
fluid, a small pipe with a tap serving to conduct the solution from 
this to a point immediately above the revolving brush. The top 
of the brush revolves towards the operator, who presents the 
object to be scratch-brushed to the bottom. The brush is sur- 
rounded by a wooden cage or screen to prevent splashing. To 



TREATMENT OF METALLIC ARTICLES. 



123 



protect the operator against the water projected by the rapid 
motion, there is fixed to the top of the frame a small inclined 
board, which reaches a little lower than the axis of the brush 
without touching it. This board receives the projected liquid, 



Fie. 




and lets it fall into a zinc trough, which forms the bottom of the 
box. Through an outlet provided in one of the angles of the 
trough a gum tube conveys the waste liquid to a reservoir below. 
After scratch-brushing every trace of the lubricating liquid must 
be washed away before placing or replacing the objects in the 
bath. 

The finished electro-plated objects are first rinsed in clean water 
to remove the solution constituting the bath adhering to them ; 
they are next immersed in hot water, where they remain until they 
have acquired the temperature of the water, and are then quickly 



124 ELECTRO-DEPOSITION" OF METALS. 

rubbed with dry, hot sawdust. It is best to use sawdust of soft 
wood, free from tannin, such as maple, poplar, or pine ; oak saw- 
dust is not suitable for the purpose on account of its content of 
tannin, which imparts a dirty coloration to the electro-deposits. 
Boxwood sawdust, though much used, is not sufficiently absorb- 
ent, and sticks to the moist objects. The sawdust used must be 
freed from coarser particles of wood by sifting. For holding the 
sawdust a zinc box with double bottom is frequently used, which 
is heated by waste steam or some other process. In order to re- 
move all moisture from the pores it is advisable to place plated 
objects of iron and steel for a few hours in an oven heated to be- 
tween 140° and 175° F. A very good method of freeing nickelled 
objects from all moisture which may have collected in the pores 
is to immerse them for about ten minutes in boiling linseed oil, 
and, after allowing them to drain off, to remove the adhering oil 
by rubbing with sawdust. According to some electro-platers, the 
deposit of nickel thus treated loses its brittleness and will stand 
bending several times, for instance, wire, sheets, etc., without 
breaking. Experiments made by Dr. George Langbein did not 
confirm these statements, but the security against rust of the 
nickelled iron objects was found to be considerably enhanced by 
boiling in linseed oil. 

The electro-plated objects, when dry, are finely polished, which 
is effected upon polishing bobs of fine felt, cloth, or flannel, with 
the use of fine rouge, Vienna lime, tripoli, etc., or by burnishing. 

Nickel deposits are almost without exception polished upon cloth 
or felt bobs with rouge or Vienna lime and oil. Copper and 
brass deposits are polished with fine flannel bobs, the polishing 
powder being applied very sparingly. Deposits of tin are gene- 
rally only scratch-brushed, it being impossible to impart great 
lustre to this metal by polishing with bobs ; after drying, the de- 
posit is polished with whiting. Deposits of gold and silver as well 
as of platinum are polished by burnishing, the steel burnisher 
being used for the grounding process, and an agate or bloodstone 
burnisher for finishing. The operation of burnishing is carried 
on as follows : Keep the tool continually moistened with soap- 
suds. Take hold of the tool very near to the end, and lean very 
hard with it on those parts which are to be burnished, causing it 



TREATMENT OF METALLIC ARTICLES. 



125 



to glide by a backward and forward motion without taking it off" 
the piece. When it is requisite that the hand should pass over a 
large surface at once without losing its point of support on the 
work bench, be careful in taking hold of the burnisher to place 
it just underneath the little finger. By these means the work is 
done more quickly, and the tool is more solidly fixed in the hand. 



Fig. 90. 




The burnishers are of various shapes to suit the requirements of 
different kinds of work, the first rough burnishing being often 
done by instruments with comparatively sharp edges, while the 
finishing operations are accomplished with rounded ones. Fig. 
90 illustrates the most common forms of burnishers of steel and 
agate. Both must be free from cracks and highly polished. To 
keep them free from blemishes they are from time to time polished 
by vigorously rubbing them with fine tin putty, rouge or calcined 
alum upon a strip of leather fastened upon a piece of wood which 
is placed in a convenient position upon the work bench. 

The objects polished with Vienna lime and oil, or with rouge, 
have to be freed from adhering polishing dirt, which, with flat 



126 ELECTRO-DEPOSITION OF METALS. 

smooth objects, is effected by wiping with a flannel rag and 
Vienna lime, and in those with depressions or dead surfaces by 
brushing with a soft brush and soap-water, and then drying in 
sawdust. 

B. Chemical Treatment. 

While the preparation of a pure metallic and, at the same time, 
smoother surface is the aim of the mechanical treatment, the 
chemical preparation of the objects serves, on the one hand, the 
purpose of facilitating the mechanical treatment by softening and 
dissolving the impure surface, and, on the other, of freeing the 
mechanically prepared objects from adhering oil, grease, dirt, etc., 
so as to bring them into the state of absolute purity required for 
the electro-plating process. 

Pickling. — The composition of the pickling fluid varies accord- 
ing to the nature of the metal which is to be pickled. 

Cast-iron and wrought-iron objects are pickled in a mixture of 

1 part by weight of sulphuric acid of 66° Be. and 15 of water; 
hydrochloric acid may be substituted for the sulphuric acid. 

An excellent pickle for iron is obtained by mixing 10 quarts 
of water with 28 ozs. of concentrated sulphuric acid,* dissolving 

2 ozs. of zinc in the mixture and adding 12 ozs. of nitric acid. 
This mixture makes the iron objects bright, while they become 
black in dilute sulphuric or hydrochloric acid. To cleanse badly 
rusted iron objects without attacking the iron itself, it is recom- 
mended to pickle them in a concentrated solution of chloride of 
tin, which, however, should not contain too much free acid, as 
otherwise the iron is attacked. 

The duration of pickling depends on the more or less thick 
layer of scale, etc., which is to be removed or softened; the 
process may be considerably assisted and the time shortened by 
frequent scouring with sand or pumice. The pickled articles are 
rinsed in cold water, then immersed in hot water, and dried in 
sawdust. In order to neutralize the acid remaining in the pores, 
it is advisable to make the rinsing water alkaline by the addition 
of caustic potash or soda, etc. 

* The acid should be poured into the water, and not the water into the aci I. 



TREATMENT OF METALLIC ARTICLES. 127 

Zinc objects are only pickled when they show a thick layer of 
oxide, in which case pickling is also effected in dilute sulphuric 
or hydrochloric acid, and brushing with fine pumice. A very 
useful pickle for zinc consists of sulphuric acid 100 parts by 
weight, nitric acid 100, and common salt 1. The zinc objects 
are immersed in the mixture for one second, and then quickly 
rinsed off in water which should be frequently changed. 

Copper and its alloys, brass, bronze, tombac, and German silver, 
are cleaned and brightened by dipping in a mixture of nitric 
acid, sulphuric acid, and lampblack, a suitable pickle consisting 
of sulphuric acid, of 6Q° Be., 50 parts by weight, nitric acid, of 
36° Be., 100, common salt 1, and lampblack 1. In order to 
remove the brown coating, due to cuprous oxide, the objects are 
first pickled in dilute sulphuric acid, and then dipped for a few 
seconds, with constant agitation, in the above-mentioned pickle 
until they show a bright appearance. They are then immediately 
rinsed in water to check any further action of the pickle. 

If objects of copper or its alloys are not to be subjected, after 
pickling, to further mechanical treatment, or are to be at once 
placed in the electro-plating bath, it is best to execute the pickling 
process in two operations by treating them in a preliminary pickle 
and brightening them in the bright-dipping bath. The prelimi- 
nary pickle consists of nitric acid, of 36° Be., 200 parts by weight, 
common salt 1, lampblack 2. In this preliminary pickle the 
articles are allowed to remain until all impurities are removed, 
when they are rinsed in a large volume of water, dipped in boil- 
ing water so that they quickly dry, and plunged into the bright- 
dipping bath, which consists of nitric acid, of 40° Be., 75 parts 
by weight, sulphuric acid, of 66° Be., 100, and common salt 1. 
It is not advisable to bring the objects which have passed through 
the preliminary pickle and rinsing water directly, while still moist, 
into the bright-dipping bath, since for the production of a beauti- 
ful pure lustre the introduction of water into the bright-dipping 
bath must be absolutely avoided. Hence the objects treated in the 
preliminary pickle should first be dried by heating in hot water, 
shaking the latter off. 

Potassium cyanide, dissolved in ten times its weight of water, 
is often used instead of the acid pickle for brass, especially when 



128 ELECTRO-DEPOSITION OF METALS. 

it is essential that the original polish upon the objects should not 
be destroyed, as in the preparation of articles for nickel-plating. 
The objects should remain in this liquid longer than in the acid 
pickle, because the metallic oxides are far less soluble in this 
than in the latter. In all cases the final cleaning in water must 
be observed. 

All acid pickles used for different kinds of work should be 
kept distinct from each other, so that one metal may not be 
dipped into a solution containing a more electro-negative metal, 
which would deposit upon it by a chemical exchange. 

The pickled objects must not be unnecessarily exposed to the 
air, and should be transferred as quickly as possible from the 
pickle to the wash waters and then to the electro-plating bath, or, 
if this is not feasible, kept under pure water. Pickled objects 
which are not to be plated are carefully washed in water, which 
should be frequently changed, rinsed, drawn through a solution of 
tartar, and dried by dipping in hot water and rubbing with saw- 
dust. 

Places soldered Math soft solder, as well as parts of iron, become 
black by pickling, and have to be brightened by scouring with 
pumice, or by scratch-brushing 

It is frequently required that bright objects of brass or other 
alloy of copper should be given a dead or dull surface by pickling, 
so that after plating they show a beautiful dead lustre. This 
maybe effected in various ways. Every bright-dipping bath acts 
as a dead dip if the articles are allowed to remain in it for a 
longer time and at a higher temperature. A better effect is, how- 
ever, produced by adding zinc sulphate (white vitriol) to the pickle, 
the deadening being the stronger the more zinc sulphate is added. 
A good dead dip is prepared by adding a solution of 0.35 oz. of 
zinc sulphate in 3J ozs. of water to the cold mixture of 6J lbs. 
of nitric acid, of 36° Be., 4.4 lbs. of sulphuric acid, of 66° Be., 
and ^ oz. of common salt. According to the shade desired, the 
articles are left in this mixture for 2 to 10 minutes, and as they 
come from it with a faded earthy appearance, they are plunged 
momentarily into a bright-dipping bath, whereby they acquire a 
dead lustre, and are then quickly rinsed in a large volume of 
clean water. 



TREATMENT OF METALLIC ARTICLES. 129 

Generally speaking, it may be said that less depends on the 
composition of the pickle than on quick and skillful manipula- 
tion ; and as good results have always been obtained with the 
above-mentioned mixture, there is no reason for repeating the 
innumerable receipts given for pickles. The main points are to 
have the acid mixture as free from water as possible, further the 
development of hyponitric acid, which is effected by the reduction 
of nitric acid in consequence of the addition of organic substances 
(lampblack, sawdust, etc.), and of chlorine which is formed by 
the action of the sulphuric acid upon the common salt. The 
volume of the dipping bath should not be too small, since in 
pickling the acid mixture becomes heated and the increased tem- 
perature shows a very rapid, frequently not controllable, action, 
so that a corrosion of small articles may readily take place. It 
is therefore necessary to allow the acid mixture, after its prepa- 
ration, to thoroughly cool off; pour the sulphuric acid into the 
nitric acid (never the reverse ! !), and allow the mixture, which 
thereby becomes strongly heated, to cool off to at least the ordi- 
nary temperature. 

In order to be sure of the uniform action of the pickle upon 
all parts, it is, in all cases, advisable previous to pickling to free 
the articles from grease by one of the methods given later on. 

In pickling abundant vapors are evolved which have an in- 
jurious effect upon the health of the workmen, and corrode metallic 
articles exposed to them. The operation should, therefore, be 
conducted in the open air, or under a well-drawing vapor flue. 

In large establishments it may happen that the quantity of 
escaping acid vapors is so large as to become a nuisance to the 
neighborhood, which the proprietors may be ordered by the autho- 
rities to abate. The evil is best remedied by a small absorbing 
plant, as follows: — 

Connect the highest point of the vapor flue D (Fig. 91) by a 
wide clay pipe R with a brick reservoir, A, laid in cement, so 
that R enters A a few centimetres above the level of the fluid, 
kept at the same height by the discharge pipe b. Above, the 
reservoir is closed by a vault through which the water conduit W 
is introduced. Below the sieve S, which is made of wood and 
coated with lacquer, a wide clay pipe R 1 leads to the chimney of 



130 



ELECTEO-DEPOSITION OF METALS. 



the steam boiler; or the suction pipe of an injector is introduced 
in this place by which the air from the vapor flue is sucked 
through the reservoir and allowed to escape into the open air or 
into a chimney. Through the manhole ill" the sieve-bottom 8 



Fig. 91. 




of the reservoir is filled with large pieces of chalk or limestone, 
the manner of operating being then as follows : A thin jet of 
water falls upon 8, where it is distributed and runs over the laye 
of chalk. The air of the pickling room saturated with acid vapor 
moves upward in consequence of the draught of the chimney oi 
the steam boiler, the injector or the ventilator, and yields its con- 
tent of acid to the layer of chalk, while the neutral solution o 
calcium nitrate and calcium chloride, which has been formed, runs 
off through b. 

The absorption of the acid vapors may, of course, be effected 
by apparatus of different construction, but the one above described 
may be recommended as being simple, cheap, and effective. 

The considerable consumption of acid for pickling purposes in 
large establishments makes it desirable to regain the acid and metal 
contained in the exhausted dipping baths. The following process 
has proved very successful for this purpose : Mix the old dipping 
baths with I their volume of concentrated sulphuric acid, and 



TREATMENT OF METALLIC ARTICLES. 131 

bring the mixture into a nitric acid distilling apparatus. Distil 
the nitric acid off at a moderate temperature, condense it in cooled 
clay-coils, and collect it in glass balloons. To the residue in the still 
add water, precipitate from the blue solution, which contains sul- 
phate of copper and zinc, the copper with zinc waste, and add 
zinc until evolution of hydrogen no longer takes place. Filter off 
the precipitated copper through a linen bag, wash and dry. The 
fluid running off, which contains zinc sulphate, is evaporated to 
crystallization and yields quite pure zinc sulphate, which may be 
sold to dye-works, or for the manufacture of zinc-white. 

According to local conditions, for instance, if the zinc sulphate 
cannot be profitably sold in the neighborhood, or zinc waste can- 
not be obtained, it may be more advantageous to omit the regain- 
ing of zinc from the dipping baths. In this case, the fluid which 
is obtained by mixing the contents of the still with water is com- 
pounded with milk of lime until it shows a slightly acid reaction. 
The gypsum formed is allowed to settle, and after bringing the 
supernatant clear fluid into another reservoir the copper is pre- 
cipitated by the introduction of old iron. The first rinsing waters 
in which the pickled objects are washed are treated in the same 
manner. The precipitated copper is washed and dried. 

For the production of a grained surface by pickling, a mixture 
of 1 volume of saturated solution of bichromate of potash in water 
and 2 volumes of concentrated hydrochloric acid may be recom- 
mended. The brass articles are allowed to remain in the mixture 
for several hours, when they are momentarily plunged into the 
bright-dipping bath, and rinsed in a large volume of water, which 
should be frequently changed. 

Removal of grease. — This operation is to be executed with the 
greatest nicety, because on it chiefly depends the success of eletrc- 
plating. Its object is to remove every trace of impurity, be it 
due to touching with the hands or to the manipulation in grind- 
ing and polishing. 

According to the preparatory treatment of the objects, the re- 
moval of grease is a more or less complicated operation. Large 
amounts of oily or greasy matter should be removed by. rinsing 
in benzine, it being recommended to execute this operation imme- 
diately after grinding and polishing so that the oil used in these 



132 ELECTRO-DEPOSITION OF METALS. 

operations has no chance of hardening as is frequently the case 
with objects polished with Vienna lime and oil. Instead of clean- 
ing with benzine, the objects, as far as their nature allows, may be 
boiled in a hot lye of 1 part of caustic potash or soda in 10 of 
water, until all the grease is saponified, when the dirt, consisting 
of grinding powder, can be readily removed by brushing. In 
place of solutions of caustic alkalies, hot solutions of potash or 
soda may be used, but their action is much slower and offers no 
advantages. Objects of tin, lead, and Britannia, being attacked 
by the hot lye, must be left in contact with it for a short time 
only. 

The articles thus freed from the larger portion of grease are 
first rinsed in water, and then for the removal of the last traces of 
grease brushed with a bristle brush and a mixture of water, quick- 
lime, and whiting, until when rinsing in water all portions appear 
equally moistened and no dry places are visible. 

The lime mixture is prepared by slaking freshly burnt lime, 
free from sand, with water to an impalpable powder, mixing 1 
part of this with ] of fine whiting, and adding water with con- 
stant stirring until a paste of the consistency of syrup is formed. 

The shape of many objects presents certain difficulties in the 
removal of grease ; the deeper portions cannot be reached with 
the brush, as, for instance, in skates, which often are to be 
nickelled in a finished state. In this case the objects are drawn in 
succession through three different benzine vessels ; in the first 
benzine most of the grease is dissolved, the rest in the second, while 
the third serves for rinsing off. When the benzine in the first ves- 
sel contains too much grease, it is emptied and filled with fresh 
benzine, and then serves as the third vessel, while that which was 
formerly the second becomes the first, and the third the second. 
After rinsing in the third benzine vessel, the objects are plunged 
in hot water, then for a few seconds dipped in thin milk of lime, 
and finally thoroughly rinsed in water. It is recommended not 
to omit the treatment with milk of lime of objects freed from 
grease with benzine. 

To avoid subsequent touching with the hands the objects, before 
freeing them from grease, must of course be tied to the metallic 
wires (of soft copper) by which they are suspended in the electro- 



TREATMENT OF METALLIC ARTICLES. 



133 



plating bath. In removing the grease by the wet method a layer 
of oxide scarcely perceptible to the eye is frequently formed upon 
the metals. This layer of oxide has to be removed, the liquid 
used for the purpose varying, of course, with the nature of the 
layer. 

Objects of iron and steel as well as of zinc are momentarily 
plunged in a mixture of sulphuric acid 1 part by weight and 
water 20 parts, and quickly rinsed off in clean water. Highly 
polished objects of iron and steel, after being treated with this 
mixture, are best again rapidly brushed with lime paste, and, after 
rinsing off quickly, immediately brought into the electro-plating 
bath. 

Copper, brass, bronze, German silver, and tombac are best 
treated with a dilute solution of potassium cyanide, 1 part of 60 



Fisj. 92. 



ill 


fir ! ^^^^^^^ 






( / %*£/'" m \ '•• 


Sg^|g7 _= 




Jk f _^^5^^^^^^^^ 


|p^iir 




-^ " ^=w ' ^i|||iiiiiii 


^^- %. 




— - ^=llp=t|ppil8Sii^ 


Wb&&T = ^~ 


— -^ ^^^M?-~ ^^ 


=3<^jf=- 


- 


^- ^ >*lr 





per cent, potassium cyanide in 15 to 20 of water. The objects 
are then quickly rinsed off and placed in the electro-plating bath. 
Lead and Britannia may be treated with water slightly acidu- 
lated with nitric acid. 



134 ELECTRO-DEPOSITION OF METALS. 

To overcome the difficult and dangerous operation of carrying 
and tilting heavy carboys containing acids, the Zucker and Levett 
Chemical Company, of New York, have introduced a simple de- 
vice whereby the carrying of carboys becomes easy, and the 
pouring out of the contents can be done with safety. The illus- 
tration, Fig. 92, shows a stand with a carboy placed thereon, 
partly swung over, as in the act of pouring. It will be seen that 
while the carboy can be tilted or turned over with ease, and any 
quantity drawn from it without the danger of spilling, a consider- 
able amount of labor and material can be saved. As seen in the 
illustration, the carrying bars are fastened or clamped to the car- 
boy by means of two screw-bolts which rest on the cleats of the 
box. These bars are of such lengths as to project beyond the 
ends of the box, and provide handles, whereby the carboy may 
be carried. The stand can be folded up in a compact manner for 
transportation or storage. 



CHAPTER VI. 

PROCESSES OF ELECTRO-DEPOSITION. 

Next to the proper mechanical and chemical preparations of 
the objects, the success of the process of electro-deposition depends 
on the suitable composition of the electrolytic solutions (baths), 
and the correct current-strength which is conducted into the bath 
for the precipitation of the metals. In regard to the latter the 
most essential conditions have already been discussed in Chap. IV., 
" Electro-plating plants in general," and will be further referred 
to in speaking of the several electro-plating processes. Hence, the 
general rules which have to be observed in the preparation of the 
baths will first be considered. 

Water being the solvent for all electrolytic baths, its constitu- 
tion is by no means of such slight importance as is frequently 
supposed. 

Spring and well water often contain considerable quantities of 
lime, magnesia, common salt, iron, etc., the presence of which may 



PROCESSES OF ELECTRO-DEPOSITION. 135 

cause various kinds of separations in the baths ; on the other 
hand, river water is frequently impregnated to such an extent with 
organic substances that its employment without previous purifica- 
tion cannot be recommended. No doubt, distilled water, or in 
want of that rain water, is the most suitable for the preparation 
of baths. However, rain water collected from metal roofs should 
not be used, nor that running off from other roofs, it being con- 
taminated with dust. Rain water should be caught in vessels of 
glass, earthenware, or wood, free from tannin, and filtered. 
Where river or well water has to be employed, thorough boiling 
and filtering before use are absolutely necessary in order to separate 
the carbonates of the alkaline earths held in solution. By boiling 
a possible content of sulphuretted hydrogen is also driven off. 

Another important factor is the purity of the chemicals used for 
the baths, the premature failure of the latter being in most cases 
caused by the unsuitable nature of the chemicals, which also fre- 
quently gives rise to abnormal phenomena inexplicable to the 
operator. Chloride of zinc, for instance, may serve as an example. 
It is found in commerce in very varying qualities, it being prepared 
for dyeing purposes with about 70 per cent, actual content of chlo- 
ride of zinc, for pharmaceutical purposes with about 90 per cent., 
and for electro-plating purposes with 98 or 99 per cent. Now 
it will readily be seen that if an operator in preparing a brass 
bath according to a formula which calls for pure chloride of zinc 
uses a preparation intended for dyeing purposes, there will be a 
deficiency of metallic zinc in the bath, and the content of copper 
in the bath being too large in proportion to the zinc present, will 
cause reddish shades in the deposits. 

Likewise, in case the operator uses potassium cyanide of low 
content, when the formula calls for a pure article with 98 per 
cent., he will not be able to effect the solution of copper or zinc 
salts with the quantity prescribed. Furthermore, potassium 
cyanide in the preparation of which prussiate of potash contain- 
ing potassium sulphate is used, will cause, by reason of the forma- 
tion of potassium sulpho-cyanide, various disturbing influences 
(formation of bubbles in the deposit), the explanation of which 
is difficult to the operator, who, trusting to the purity of the 



136 ELECTKO-DEPOSITION OF METALS. 

chemicals, seeks elsewhere for the causes of the abnormal phe- 
nomena. 

Or, if in preparing nickel baths, a salt containing copper is 
used, the nickelling will never be of a pure white color, but show 
shades having not even a distant resemblance to the color of 
nickel. 

The above-mentioned examples suffice to show how careful the 
operator must be in the selection of the sources from which he ob- 
tains his supplies. It may here be mentioned that all the direc- 
tions given in the following pages refer to chemically pure pro- 
ducts ; where products of a lower standard may be used the 
content is especially given. 

For the concentration of the various baths, no general rules can 
be laid down ; neither can the determination of the density of the 
baths by the hydrometer be relied on. If the electro-plating 
solutions consisted of nothing but the pure metallic salts, the 
specific gravity, which is indicated by the hydrometer-degrees, 
might serve for an estimation of their value. But such an esti- 
mation is often apt to prove deceptive, since to decrease the resist- 
ance the baths also require conducting salts, and by the addition 
of a larger quantity of them the specific gravity of a bath may 
be increased to any extent without the content of the more valu- 
able metal being greater than in a bath showing fewer hydrometer- 
degrees. 

An electrolytic bath should not be poor in metal, as otherwise 
it soon becomes exhausted, and besides the deposits form more 
slowly than in a bath with a correct content of metal ; on the 
other hand, the bath must not be too concentrated, as, in this 
case, salts in the form of crystals readily separate and deposit 
themselves upon the anodes, the sides of the vessels, and even 
upon the articles themselves, which may cause holes to form in 
the deposit ; or the crystals envelop the anodes so tightly that the 
current cannot reach the bath. Besides, too concentrated baths 
generally produce discolored deposits, as, for instance, too concen- 
trated nickel baths, which yield a dark and spotted deposit. 

Hence in summer, when the bath has a higher temperature, it 
may be made more concentrated than in winter. If crystals are 
separated out, even when the bath shows a temperature of 58° F., 



PEOCESSES OF ELECTRO-DEPOSITION. 137 

it must be diluted with water until the formation of crystals 
ceases, after those which have been formed have been dissolved in 
hot water added to the bath. 

In order that all strata of the bath may show an equal content 
of metal, it is advisable in the evening, after the day's work is 
done, to thoroughly stir up the solution with a wooden crutch. 
For practical reasons the baths are generally made one-quarter to 
one-third deeper than corresponds to the lengths of the objects to 
be plated. In consequence of this, the strata of fluid between 
the anodes and the objects become poorer in metal than those on 
the bottom, and the object of stirring up is to restore the same 
concentration to all portions of the bath. 

The strata of fluid which come in contact with the anodes 
become, by the absorption of metal, specifically heavier than the 
other strata, and sink to the bottom ; on the other hand, the strata 
of fluid which yield metal to the objects become specifically lighter 
and rise to the top. A partial compensation of course takes place 
by diffusion, but not a complete one, and from this cause arise 
several evils. The heavier and more saturated fluid, offering 
greater resistance to the current, the anodes are attacked chiefly 
on the upper portions where the specifically lighter layer of fluid 
is; practically this is proved by the appearance of the anodes 
which, at first square, after being for some time used 
assume the shape shown in Fig. 93. 

On the other hand, the portions of the cathodes 
(objects) which come in contact, near the surface, 
with strata of fluid poorer in metal, acquire a deposit 
of less thickness than the lower portions which dip 
into the bath where it is richer in metal. Now, if 
the bath also contains free acid, and if there is a con- 
siderable difference in the specific gravity of the lower 
and upper strata of fluid, the electrode, which touches 
both strata, produces a current, the effect of which is that metal 
dissolves from the upper portions and deposits upon the lower. 
This explains the phenomenon that a deposit on the upper por- 
tions of the objects may be redissolved, even when a current 
which, however, must be very weak, is conducted into the bath 
from an external source. 




138 ELECTRO-DEPOSITION OF METALS. 

Many authors, therefore, go so far as to demand that during 
the electro-plating process the baths should be kept in constant 
agitation by mechanical means. This, however, is scarcely neces- 
sary, because a homogeneity of the solution is to a certain extent 
effected by the agitation of the fluid in suspending and taking 
out the objects. Hence as long as objects are put in and taken 
out an agitation naturally takes place in which all the strata of 
fluid between the objects and anodes take part, while only the 
deepest strata, which do not come into contact with the objects 
and the anodes, remain in a state of stagnation. 

Constant agitation of the electro-plating solution is of advantage 
only in silvering and in the galvano-plastic reproduction in the 
acid copper bath, in which the objects have to remain four to five 
and eight to ten hours. Some authors demand constant agitation 
for the more rapid removal of the bubbles of hydrogen which form 
on the objects ; but the same end is attained without complicated 
contrivances, by the operator accustoming himself to strike the ob- 
ject-rod a slight blow with the finger each time he suspends an object. 

The degree of temperature required for the electro-plating solu- 
tions has already been discussed on page 76, where also the means 
have been given by which too cool solutions may be brought to 
the proper degree of temperature. Baths which are to be used cold 
should under no circumstances show a temperature below 59° F., 
it being best to maintain them at between 64.5° and 68° F. 

Boiling is required in the preparation of many baths, if, after 

Fig. 94. 




V J 

cooling, they are to yield good and certain results. The kettles 
and boiling-pans used for the purpose are of various shapes, 
hemispherical or with flat bottom, and are made of different 
materials (Figs. 94 and 95), those of enamelled iron, or, for small 
baths, of porcelain or earthenware, being best. The enamel of 



PROCESSES OF ELECTRO-DEPOSITION". 139 

the iron kettles must be of a composition which is not attacked by 
the bath. Notwithstanding their enamel these vessels become 
gradually impregnated with the solutions they have held, and it 
is dangerous to employ them for different kinds of baths. Thus, 
an enamelled kettle which has been used for silvering will not be 
suitable, even after the most thorough washing, for a gold bath, 
as the gilding will certainly be white or green, according to the 
quantity of silver retained by the vessel. The use of metal 
vessels should be avoided ; copper and brass baths may, however, 
be boiled in strong copper kettles, though they are somewhat 
attacked. A copper kettle, after being freed from grease and 
scoured bright, may be provided with a thick deposit of nickel, 
by filling it with a nickel bath, connecting it with the negative 
pole of a strong battery or dynamo machine, and suspending in it 
a number of nickel anodes connected with the positive pole. 
Such nickelled kettle may be used for boiling nickel baths, but 
enamelled kettles or large dishes of nickel-sheet deserve the 
preference. 

If the boiling of large quantities of fluid is not convenient, 
the same end may be attained by thoroughly working the bath 
for a few days with the electric current. Suspend to the anode- 
rods as many anodes as possible, secure to the object-rods a few 
plates of the same metal, and introduce a current of medium 
strength, until an object, from time to time, suspended in the bath 
acquires a regular deposit. This method is frequently and very 
successfully used for large brass baths. 

If nickel salts, dissolving with difficulty, have to be dissolved 
for the preparation of nickel baths, and a suitable kettle for the 
purpose be wanting, boil clean water in a brightly-scoured copper 
kettle ; pour the boiling water into a clean wooden bucket holding 
from eight to ten quarts; add the corresponding quantity of nickel 
salt, and stir with a stick of wood until solution is complete. 

For large baths this method consumes too much time, and it is 
better to use a large oval or round wooden vat, which is provided 
with a coil of lead, and to bring the contents of the vat to boiling 
by introducing steam into the coil. 

If the prepared and boiled solutions are not entirely clear, 
they have to be filtered, which for large baths is best effected 



140 ELECTRO-DEPOSITION OF METALS. 

with bags of fine felt; and for smaller baths, especially those of 
the noble metals, with filtering paper. 

To secure lasting qualities to the baths, they must be carefully 
protected from every possible contamination. When not in use 
for plating they should be covered to keep out dust. The objects 
before being placed in the baths should be free from adhering 
scouring material or dipping fluid, which otherwise might, in time, 
spoil the bath. The cleansing of the anode and object rods by 
means of sand paper, or emery paper, should never be done over 
the bath, so as to avoid the danger of the latter being con- 
taminated by the oxides of the metal constituting the rods falling 
into it. When a visible layer of dust has collected upon the 
bath, it must be removed, as otherwise particles of dust might 
deposit upon the articles and prevent an intimate union of the 
deposit with the basis-metal. With large baths the removal of 
the layer of dust is readily effected by drawing a large piece of 
filtering or tissue paper over the surface, and repeating the opera- 
tion with fresh sheets of clean paper until all the dust is removed. 
Small baths should be filtered. 

The choice of anodes is also an important factor for keeping 
the baths in good condition, as well as for obtaining good results. 
The anodes should always consist of the metal which is deposited 
from the solution ; and the metal used for them must be pure and 
free from all admixtures. To replace as much as possible the 
metal withdrawn from the bath by the electro-plating process, the 
anodes must be soluble ; and it is wrong if, for instance, nickel 
baths are charged with insoluble anodes of carbon ; or for smaller 
baths, of sheet platinum. Such insoluble anodes cause a steady 
and rapid declination in the content of metal, an excessive forma- 
tion of acid in the bath, and, by the detachment of particles of 
carbon, a contamination of the solution. Further particulars in 
regard to anodes will be given in discussing the separate baths. 

When upon a pure metallic surface another metal is electro- 
deposited, the first portion of the deposit penetrates into the basis- 
metal, thus forming an alloy. This may be readily proved by 
repeating Gore's experiments : If a thick layer of copper be pre- 
cipitated upon a platinum sheet, aud then heated to a dark red 
heat, the deposit can be entirely peeled off; by then heating the 



PROCESSES OF ELECTRO-DEPOSITION. 141 

platinum sheet with nitric acid, and thoroughly washing with 
water, it appears, after drying, entirely white and pure. By re- 
heating the sheet, the surface becomes again blackened by cupric 
oxide, and by frequently repeating the same operation a fresh 
film of cupric oxide will always be obtained. 

This penetration of the deposit into the basis-metal, however, 
does not merely take place during electro-plating but also later 
on, and it may frequently be observed that, for instance, zinc 
objects only slightly coppered or brassed, after some time become 
again white. Since this also happens when the deposits are pro- 
tected by a coat of lacquer against atmospheric influences, the 
only explanation of the phenonenon can be that the deposit is 
absorbed by the basis-metal, which is also confirmed by analysis. 
This fact must be taken into consideration if durable deposits are 
to be produced. 

To guarantee good performance an electro-plating bath must 
fulfil the following conditions : — 

1. It must possess good working capacity. 

2. If must exert a sufficiently dissolving action upon the anode. 

3. It must reduce the metal in abundance and in a reguline 

state. 

4. It must not be chemically decomposed by the metals to be 

plated, hence not by simple immersion ; the adherence of 
the deposit to the basis-metal being in this case impaired. 

5. It must not be essentially decomposed by air and light. 

Reduction of metals without a battery (electro-deposition by contact). 

We may here appropriately mention the reduction of metals 
which takes place by the contact of two metals in a fluid without the 
aid of an exterior source of current. That an electric current is 
thereby generated has been previously explained : one metal, by 
coming in contact with a more electro-positive one, becomes 
electro-negative and decomposes the fluid. If the latter is a 
metallic solution, and the metal contained in it not more strongly 
electro-negative than the negatively excited metal, a separation 
of metal takes place in consequence of decomposition. This pro- 
cess is termed electro-deposition by contact. Generally the metals 



112 



ELECTRO-DEPOSITION OF METALS. 



which are to be coated are brought in contact with a bright rod of 
zinc, the latter being a highly electro-positive metal. The zinc 
is allowed to dip in only so far as to secure a sure contact with 
the metal to be coated. 

The contact of one metal with two fluids, or that of two metals 
in two fluids, presents similar phenomena ; an electric current with 
visible action manifests itself, and in the latter case we have a com- 
plete element. By dipping the more electro-negative metal in a 
metallic solution whose metal is not more electro-negative, the 
metal separates from the solution upon the metallic strip clipping 



Fig. 96 



Fig. 97. 





Fig. 98. 



Fig. 99. 





in. While by the contact of one metal with another in one fluid, 
only thin deposits can be produced, and by coating the electro- 
negative metal with the separated metal the contact-current loses 
some of its original strength, by immersing two metals in two 



DEPOSITION OF NICKEL AND COBALT. 143 

fluids, depositions of considerable thickness can under certain con- 
ditions be produced, as, for instance, with the galvano-plastic cell 
apparatus, which will be discussed later on. 

A reduction of metal can also be brought about by dipping one 
metal into one fluid. This may take place in consequence of the 
simple solution of the metal dipped in, and hence the separation 
may be conceived as a simple chemical action. In how far electric 
currents manifest themselves and co-operate thereby is still unde- 
cided ; we only know that the electro-positive metals, such as 
zinc, tin, iron, copper, can reduce the electro-negative metals, such 
as mercury, silver, gold, etc., from the solutions of their salts, and 
that the reduction is the more rapid and the stronger the more 
electro-positive is the metal dipped in, and the more electro- 
negative the dissolved metal. 

Upon this action depend coppering, silvering, gilding, etc., by 
immersion. 

For dipping large numbers of small articles at a time dipping- 
baskets are used. Figs. 96 to 99 represent different forms of glazed 
stone- ware dipping- baskets such as are generally employed, though 
some platers prefer a platinum gauze cage. 



CHAPTER VII. 

DEPOSITION OP NICKEL AND COBALT. 

1. Niokelling, 

Though nickel-plating is of comparatively recent origin, it 
shall be first described, since chiefly by reason of the development 
of the dynamo-electrical machine it has steadily grown in popu- 
larity and become an industry of great magnitude and impor- 
tance. The great popularity which nickel-plating enjoys is due to 
the excellent properties of the nickel itself: the almost silvery 
whiteness of the metal, its cheapness as compared with silver, and 
the hardness of the electro-deposited metal, which give the coat- 
ing great power to resist wear and abrasion, its capability of tak- 
ing a high polish ; the fact that it is not blackened by the action 



144 ELECTRO-DEPOSITION OF METALS. 

of sulphurous vapors which rapidly tarnish silver, and finally the 
fact that it exhibits but little tendency to oxidize even in the 
presence of moisture. 

Properties of nickel. — Pure nickel is a lustrous, silvery white 
metal with a slight steel gray tinge. It is hard, malleable, and 
ductile. Its specific gravity varies from 8.3 (cast nickel plates) to 
9.3 (wrought or rolled plates). It melts at about the same tem- 
perature as iron, but is more fusible when combined with carbon. 
It is slightly magnetic at ordinary temperatures, but loses this 
property on heating to 680° F. 

The metal is soluble in dilute nitric acid, concentrated nitric 
acid rendering it passive, i. e., insoluble. In hydrochloric and 
sulphuric acids it dissolves very slowly, especially when in a com- 
pact state. 

Certain articles, for instance, hot fats, strongly attack nickel, 
while vinegar, beer, mustard, tea, and other infusions produce 
stains • hence, the nickelling of culinary utensils or the use of 
nickel-plated sheet-iron for culinary utensils cannot be recom- 
mended. 

The chemical equivalent of nickel is 29.5 

Nickel baths. — The first requisite in preparing nickel baths is 
the use of absolutely pure chemicals, and in choosing the nickel 
salts to be especially careful that they are free from salts of iron, 
copper, and other metals. Furthermore, it is not indifferent what 
kind of nickel salt is used, whether nickel chloride, nickel sul- 
phate, the double sulphate of nickel and ammonium, etc., but the 
choice of the salt depends chiefly on the nature of the metal 
which is to be nickelled. There are a large number of general 
directions for nickel baths, of which nickel chloride, ammonio- 
nickel chloride, nickel nitrate, etc., form the active constituents, 
and yet it would be a grave mistake to use these salts for nickel- 
ling iron, because the liberated acid, if not immediately and com- 
pletely fixed by the anodes in dissolving, imparts to the iron 
objects a great tendency to the formation of rust. Iron objects 
nickelled in such a bath, to be sure, come out faultless, but in a 
short time, even if stored in a dry place, portions of the nickel 
layer will be observed to peel off, and by closely examining such 
objects it will be seen that under the deposit of nickel a layer of 



DEPOSITION OF NICKEL AND COBALT. 145 

rust has formed which actually tears the nickel off. The use of 
nickel sulphates or of the salts with organic acids is, therefore, 
considered best. It might be objected that the liberated sul- 
phuric acid produces in like manner a formation of rust upon the 
iron objects, but according to long experience and many thorough 
examinations such is not the case, the tendency to the formation 
of rust being only imparted by the use of the chloride and nitrate. 
The use of nickel salts with organic acids is in many cases more 
advantageous than that of the sulphates, but such salts are con- 
siderably dearer, and hence they are less frequently employed ; in 
many prepared nickelling salts they form the active constituent. 
The composition of the conducting salts requires the same deliber- 
ation as that of the nickelling salts. To decrease the resistance 
of the nickel solutions, conducting salts are added to them, which 
are also partially decomposed by the current. Like the use of 
nickel chloride in nickelling iron, an addition of ammonium 
chloride, which is much liked, cannot be recommended, though 
the subsequent easy reduction of nickel invites its employment. 

For copper and its alloys, zinc, etc., the chlorine combinations 
may be used, but for nickelling iron they must be avoided as the 
source of future evils. The use of sodium sulphide, sodium 
nitrate, barium oxalate, ammonium nitrate, sodium sulphate, and 
ammonium-alum as conducting salts, which has been recom- 
mended by various authors, is unsuitable. With few exceptions, 
which will be given later on, the best basis for the conducting 
salt, according to Bottger and Adams, is ammonia, especially in 
the form of ammonium sulphate or hydrochlorate, provided the 
latter is not used for baths for nickelling iron. 

Some other additions to the nickelling bath which are claimed 
to effect a pure silvery-white reduction of the nickel have been 
recommended by various experts. Thus, the presence of small 
quantities of an organic acid has been proposed ; for instance, boric 
acid by Weston, benzoic acid by Powell, and citric acid or acetic 
acid by others. The presence of small quantities of a free acid 
effects without doubt the reduction of a whiter nickel than is 
the case with a neutral or alkaline solution. Hence a slightly 
acid reaction of the nickelling bath, due to the presence of citric 
acid, etc., with the exclusion of the strong acids of the metal- 
10 



146 ELECTEO-DEPOSITION OF METALS. 

loids, can be highly recommended. The quantity of free acid 
must, however, not be too large, as this would cause the deposit 
to peel off. 

Boric acid, recommended by Weston as an addition to nickel- 
ling and all other baths, has a favorable effect upon the pure white 
reduction of the nickel, especially in nickelliug rough castings, 
i. e., surfaces not ground. Weston claims that boric acid pre- 
vents the formation of basic nickel combinations on the objects, 
and that it makes the deposit of nickel more adherent, softer, 
and more flexible. Whether with a correct current-strength, 
basic nickel salts, to which the yellowish tone of the nickelling is 
said to be due, are separated on the cathode, is not yet proved, 
and would seem more than doubtful. The action of the boric 
acid has not yet been scientifically explained, but numerous ex- 
periments have shown that the deposition of nickel from nickel 
solution containing boric acid is neither more adherent nor softer 
and more flexible than that from a solution containing small quan- 
tities of a free organic acid. Just the contrary, the deposition is 
harder and more brittle in the presence of boric acid, and differ- 
ent results may very likely be due to the employment of currents 
of varying strength. A weak current always and under all con- 
ditions causes the deposition of a harder and more brittle nickel 
than a current of medium strength, and in order to judge the 
quality of the deposited nickel from baths of varying composition, 
the surface of the objects and of the anodes must always be the 
same, and currents of equal quantity and electro-motive force be 
conducted into the bath. Weston's bath will be spoken of later 
on. Powell's proposition for the use of benzoic acid need scarcely 
be taken seriously, since the results from baths containing it 
differ in no respect from those without it. 

Before giving suitable formulae for the composition of nickel 
baths, it will be necessary to discuss the means of determining 
their acidity and alkalinity. As previously mentioned, a nickel 
bath, to yield a beautiful white deposit, should contain only a 
small quantity of free acid ; too much acid preventing the firm 
adherence of the deposit, while alkaline and even neutral baths 
do not yield nickel of a pure white color, but of a somewhat 
darker tone. A bath is neutral when it contains neither free acid 



DEPOSITION OF NICKEL AND COBALT. 147 

nor free alkali, which is recognized by neither blue nor red litmus- 
paper* being changed by the solution. Blue litmus-paper is 
colored red by acid fluids, and red litmus-paper blue by alkaline 
fluids. By simultaneously dipping one-half of a strip of blue 
and of red litmus-paper in the solution, the reaction of the fluid 
can be judged from the change in color and the rapidity and 
intensity of its appearance. If a bath which, like most nickel 
baths, is to work with only a slight reaction, immediately and 
intensely reddens blue litmus-paper, a suitable alkali has to be 
added until the coloration of a fresh strip of litmus-paper appears 
slower and less intense. If, on the other hand, the test shoves 
that red litmus-paper becomes blue, and that consequently the 
bath is alkaline, a slight acid reaction is restored by the gradual 
addition of citric acid or another acid suitable to the composition 
of the bath. Baths made with boric acid form an exception, and 
must work with a strong acid reaction. 

I. The most simple nickel bath consists of a solution of 8 to 10 
parts by weight of pure nickel ammonium sulphate in 100 parts 
by weight of distilled water. If too acid, the solution is neutral- 
ized with spirits of sal ammoniac to a slightly acid reaction. The 
solution is prepared by boiling the salt with the corresponding 
quantity of water, using in summer 10 parts of nickel salt to 100 
of water, but in winter only 8 parts, to prevent the nickel salt 
from crystallizing out. This bath, which is frequently used, 
possesses, however, a considerable degree of resistance to conduc- 
tion, and hence requires a strong current for the deposition of 
the nickel. It also requires cast nickel anodes, since with the 
use of rolled anodes nickelling proceeds in a very sluggish man- 
ner. However, the cast anodes rapidly render the bath alkaline, 
necessitating a frequent correction of the reaction. To decrease 
the resistance, recourse has been had to certain conducting salts, 
and, below, the more common nickel baths will be discussed, 
together with their mode of preparation and action, as well as 
their availability for certain purposes. 

II. Nickel ammonium sulphate 17 ozs., ammonium sulphate 
17 ozs., distilled water 10 quarts. 

* Blue and red litmus-paper must be kept, each by itself, in well-closed 
glass jars. 



148 ELECTRO-DEPOSITION OF METALS. 

Boil the salts with the water, and, if the solution is too acid, 
restore its neutrality by spirits of sal ammoniac ; then gradually 
add solution of citric acid until blue litmus-paper is slowly but 
visibly reddened. The bath deposits rapidly, it possessing but 
little resistance; an electro-motive force of 1.8 to 2 volts suffices, 
and all metals (zinc, lead, tin, and Britannia, after previous cop- 
pering) can be nickelled in this bath. However, upon rough 
castings and iron a pure white deposit is difficult to obtain, fre- 
quent scratch-brushing with a medium hard steel brush being 
required. On account of the great content of sulphate of am- 
monium in the bath, the nickel deposit piles up especially on the 
lower portions of the objects, which, in consequence, readily be- 
come dull (burn or over-nickel, for which see later on), while the 
upper portions are not sufficiently nickelled. For this reason the 
objects must be frequently turned in the bath so that the lower 
portions come uppermost. This piling up of the deposit also 
frequently prevents the latter from acquiring a uniform thickness. 

III. Nickel ammonium sulphate 25| ozs., ammonium sulphate 
8 ozs., crystallized citric acid If ozs., water 10 to 12 quarts. 

This bath is prepared in the same manner as the preceding, the 
salts being dissolved in boiling water, and ammonia added until 
blue litmus-paper is only slightly reddened. 

This bath requires a somewhat greater electro- motive force 
than the preceding, or about 2 to 2.2 volts. The formation 
of the nickel deposit is, however, more uniform, of a beautiful 
white color, dense and hard, and consequently bears polishing 
without danger of the nickel grinding off, even if not very thickly 
plated. It is very suitable for nickelling ground surgical instru- 
ments, as well as all ground iron articles which are to be thickly 
and solidly plated, and for heavy, solid nickelling of copper, brass, 
bronze, etc. It is much used in this country, either with or with- 
out the addition of citric acid. 

If, after working for some time, the bath loses conducting 
power, the objects, with the use of the proper current, become 
blackish without a reduction of nickel being perceptible ; while 
with a stronger current the objects are nickelled white, but the 
deposit readily peels off. In this case the conducting power 
has to be increased by the addition of ammonium sulphate. 



DEPOSITION OF NICKEL AND COBALT. 149 

The bath should always be kept so that it shows a slightly acid 
reaction. It is best to use rolled anodes. 

IV. Nickel ammonium sulphate 23 ozs., ammonium chloride 
(crystallized) 11^ ozs., water 10 to 12 quarts. 

The bath is prepared in the same manner as given for II. 
and III. It nickels very rapidly and quite white, but the deposit 
is soft, and hence care must be had in polishing upon cloth or 
felt bobs, the corners and edges of the objects especially requiring 
careful handling. On account of the danger of peeling off, a 
heavy deposit of nickel cannot be obtained in this bath, since, in 
consequence of the rapid precipitation, the deposit condenses and 
absorbs hydrogen, is formed with a coarser structure, and turns 
out less uniform and dense. These phenomena are a hindrance 
to a heavy deposit, which, if it is to adhere, must be homogeneous 
and dense. As previously mentioned, baths with the addition of 
chlorides as well as those prepared with nickel chloride and nickel 
nitrate are not suitable for the solid nickelling of iron ; they are, 
however, well adapted to the rapid light nickelling of cheap brass 
articles. The electro-motive force required for this bath is 1.8 
volts. 

V. Nickel chloride (crystallized) 17 J ozs., ammonium chloride 
(crystallized) 17 J ozs., water 12 to 15 quarts. 

The bath is prepared in the same manner as given for II. and 
III., though solution may be effected cold. The bath precipi- 
tates very readily, and is especially liked for nickelling zinc cast- 
ings. Tension of current, 1.5 to 1.75 volts. 

For nickelling iron this bath has the same disadvantages, and 
even to a still greater extent than the preceding. 

VI. Baths containing boric acid. — Weston recommends the 
following composition for nickel baths : Nickel chloride 17J ozs., 
boric acid 7 ozs.; water 20 quarts, or, nickel-ammonium sulphate 
35 ozs., boric acid 17 J ozs., water 25 to 30 quarts. Both solu- 
tions are said to be improved by adding caustic potash or caustic 
soda so long as the precipitate formed by the addition dissolves.* 

These compositions, however, cannot be recommended, chiefly 
because the baths work faultlessly for a comparatively short time 
only ; all kinds of disturbing phenomena make their appearance, 

* Dingler's Journal, 235, p. 404. Wagner's Jahresberieht, 1883, p. 146. 



150 ELECTRO-DEPOSITION OF METALS. 

the deposit being no longer white but blackish, and the baths soon 
failing entirely. Kaselowsky's formula yields similar results. It 
is prepared by dissolving, with the assistance of heat, 35J ozs. of 
nickel-ammonium sulphate and 17§ ozs. of boric acid in 20 quarts 
of water. If an entirely neutral double sulphate has not been 
employed, this bath also generally fails after two or three months' 
use. By taking the ordinary nickel salt, which is crystallized 
from an acid solution and employing rolled nickel anodes, the 
bath will certainly have to be thrown away after using it at the 
utmost for three months. 

Such a bath, with boric acid, however, works satisfactorily by 
proceeding as follows : — 

VII. Nickel-ammonium sulphate 21 ozs., chemically pure 
nickel carbonate If ozs., chemically pure crystallized boric acid 
10J ozs., water 10 to 12 quarts. 

Boil the nickel-ammonium sulphate and the nickel carbonate 
in the water until the development of bubbles of carbonic acid 
ceases and blue litmus-paper is no longer reddened ; then add 
the boric acid, and after allowing the whole to boil a few minutes 
longer cool and filter. The reaction of the solution is strongly 
acid and must not be removed by alkaline additions. A bath 
thus prepared lasts at least twice as long as one which is pre- 
pared without previous neutralization of the double nickel salt 
by nickel carbonate. The treatment of the bath varies according 
to whether rolled or cast anodes are used ; in the first case free 
sulphuric acid readily forms, the consequence of which will 
be an exfoliating reduction of nickel with a simultaneous 
strong evolution of hydrogen on the objects. The bath must 
then be compounded with an addition of alkali (except spirit 
of sal ammoniac) corresponding to the quantity of free sul- 
phuric acid. With the use of cast anodes the bath readily be- 
comes alkaline, and requires the restoration of the acid reaction, 
since a bath containing boric acid, which has become alkaline, 
also nickels gray-black and dull, even when the deposit has ac- 
quired only slight thickness. It is, therefore, best to work with 
mixed anodes, i. e. , rolled and cast. 

A bath prepared according to the above formula requires an 
electro-motive force of about 2.5 volts; while working, the resist- 



DEPOSITION OF NICKEL AND COBALT. 151 

anceof the solution increases somewhat and reaches its maximum 
in 3 or 4 weeks, when it remains constant. All baths prepared 
with an addition of boric acid exhibit the property of their resist- 
ance growing with comparative rapidity in the beginning, but 
not increasing after having reached a certain limit. 

Below are given a few other formulae for nickel baths which 
may be advautageously used for certain purposes, but not for 
nickelling all kinds of metals. 

VIII. Nickel sulphate 10J ozs., potassium citrate 7 ozs., 
ammonium chloride 10J ozs., water 10 to 12 quarts. 

To prepare the bath dissolve 10| ounces of nickel sulphate and 
3| ounces of pure crystallized citric acid in water ; neutralize accu- 
rately with caustic potash, and then add the ammonium chloride. 
This bath is especially adapted for the rapid nickelling of polished, 
slightly coppered zinc articles. The deposition is effected with a 
very feeble current, without the formation of black streaks, such 
as are otherwise apt to appear in nickelling with a weak current. 
The deposit itself is dull and somewhat gray, but acquires a very 
fine polish and pure white color by slight manipulation upon the 
polishing wheels. With a stronger current the bath is also suita- 
ble for the direct nickelling of zinc articles ; it must, however, be 
kept strictly neutral. The bath works with rolled anodes, and 
but seldom requires a correction of the reaction. 

IX. Nickel phosphate 8J ozs., sodium pyrophosphate 26^ ozs., 
water 10 to 15 quarts. Dissolve the sodium pyrophosphate in 
water, heat the solution to about 167° F. and add the nickel phos- 
phate with constant stirring. Nickel phosphate is obtained as a 
pale green powder by precipitating solution of nickel sulphate 
with sodium phosphate. 

This bath yields a very fine dark nickelling upon iron, brass, and 
copper, as well as directly, without previous coppering, upon sheet 
zinc and zinc castings, and may be advantageously used for deco- 
rative purposes where darker tones of nickel are demanded. 

X. A fairly good nickel-bath for electro-platers having but a 
feeble current at their disposal is obtained from a solution of nickel- 
ammonium sulphate 22 \ ozs., magnesium sulphate \\\ ozs., water 
10 to 12 quarts. 

This bath precipitates readily and strongly, and a heavy coating 



152 ELECTEO-DEPOSITION OF METALS. 

can also be deposited upon iron without fear of the disagreeable 
consequences of bath IV.; even zinc may be directly nickelled in 
it with a comparatively feeble current. The deposit, however, 
turns out rather soft, with a yellowish tinge, and the bath does not 
remain constant, but fails after working at the utmost three or 
four months, the anodes being scarcely attacked. 

Below are given the compositions of a few nickel baths which 
have recently been highly recommended : — 

XL Pure nickel sulphate 35J ozs., neutral ammonium tartrate 
26J ozs., tannin 77 grains, water 20 quarts. Neutral ammonium 
tartrate is obtained by saturating a solution of tartaric acid with 
ammonia. The nickel salt must also be neutral. For this pur- 
pose dissolve the above-mentioned ingredients in 3 or 4 quarts of 
water and boil the solution for \ hour, then add enough water to 
make 20 quarts of fluid, and filter. The bath is said to yield a 
very white, soft, and homogeneous deposit of any desired thickness, 
without roughness or danger of peeling off. On rough or polished 
castings thick deposits may be obtained at a cost scarcely exceeding 
that of coppering. Galvanoplastic reproduction may also be 
effected in this bath. For those who wish to try the bath it may 
be mentioned that the most suitable current-strength is 3.5 volts. 

XII An English formula is as follows : Dissolve 17 \ ozs. of 
nickel sulphate, 9 \ ozs. of tartaric acid, and 2 \ ozs. of caustic potash 
in 10 quarts of water. 

The addition of bisulphide of carbon to nickel baths, which 
has recently been recommended by Bruce, is not advisable. Ac- 
cording to Bruce, such an addition prevents the nickel deposits 
from becoming dull when reaching a certain thickness, but re- 
peated experiments made strictly in accordance with the directions 
given did not confirm this statement. 

XIII. For nickelling small articles the following bath is claimed 
to yield excellent results : Nickel-ammonium sulphate 64 ozs., 
ammonium sulphate 20| ozs., crystallized citric acid 4J ozs. 

In some works on galvanoplasty a solution of nickel cyanide in 
potassium cyanide is recommended for nickelling, but experiments 
failed to obtain a proper reduction of nickel. 

We would here add the general remark that freshly prepared 
nickel baths mostly work correctly from the beginning, though it 



DEPOSITION OF NICKEL AND COBALT. 153 

may sometimes happen that the articles first nickelled come from 
the bath with a somewhat darker tone. In such case it is advis- 
able to suspend a few anodes to the cathode and allow the bath 
to work one or two hours, when the nickelling will proceed fault- 
lessly. 

A few words may here be said in regard to what may be termed 
a nickel bath without nickel salt. It simply consists of a 15 to 20 
per cent, solution of ammonium chloride, which transfers the nickel 
from the anodes to the articles; cast anodes are almost exclu- 
sively used for the purpose, and deposition may be effected with 
quite a feeble current. Before the solution acquires the capacity 
of depositing, quite a strong current has to be conducted through 
the bath until the commencement of a proper reduction of nickel. 
This bath is only suitable for coloring very cheap articles, it not 
being possible to produce solid nickelling with it, and it is here 
mentioned because it may serve as a representative of a series of 
other electro-plating baths in which the transfer of the metal is 
effected by sal ammoniac solution without the use of metallic 
salts, for instance, iron, zinc, cobalt, etc. 

Nickel anodes. — Either cast or rolled nickel plates are used as 
anodes, which must of course be as pure as it is possible to obtain 
them. Every impurity of the anodes passes into the bath and 
jeopardizes its successful working. If too thin, the anodes in- 
crease the resistance ; for small baths rolled anodes 0.079 inch 
thick are generally used, and as a rule they should not be less 
than 0.039 inch thick. For larger baths it is better to use plates 
from 0.11 to 0.19 inch thick, while the thickness of cast anodes 
may vary between 0.11 and 0.39 inch, according to the size of the 
bath and the purpose for which it is to be used. The use of 
insoluble anodes of gas-carbon or platinum, either by themselves 
or in conjunction with nickel anodes, as frequently recommended, 
is not advisable. The harder and the less porous the nickel anode 
is, the less it is attacked in the bath and the less it fulfills the ob- 
ject of keeping constant the metallic content of the solution. On 
the other hand, the softer and the more porous the anode is, the 
more readily it dissolves, because it conducts the current better 
and presents more points of attack to the bath ; and the more it 
is dissolved, the more metal is conveyed to the bath. With the 



154 ELECTRO-DEPOSITION OF METALS. 

sole use of rolled anodes and working with a feeble current, free 
acid is formed in the bath ; on the other hand, by working with 
cast anodes alone, the bath readily becomes alkaline. Now it 
seems that the possibility of a bath also becoming alkaline 
even with the sole use of rolled anodes, especially when work- 
ing with a strong current, has led to the proposal of suspend- 
ing in the bath, besides the nickel anodes, a sufficient number 
of insoluble anodes in order to effect a constant neutrality of 
the bath. It would lead too far to go into the theory of the 
secondary decompositions which take place in a nickel bath, to 
prove that, though neutrality is obtained, it can only be done at 
the expense of the metallic content of the bath. Hence, this im- 
practicable proposal shall here be overthrown by practical reasons, 
it only requiring to be demonstrated that in baths becoming alka- 
line the content of nickel also decreases steadily though slowly. 
This fact in itself shows that in order to save the occasional slight 
labor of neutralizing the bath, the decrease of the metallic con- 
tent should not be accelerated by the use of insoluble anodes. 
For larger baths the use of expensive platinum anodes as in- 
soluble anodes need not be taken into consideration, because for 
large surfaces of objects correspondingly large surfaces of plati- 
num anodes would have to be present, as otherwise the resistance 
of thin platinum sheets would be considerable. But such an ex- 
pensive arrangement would be justifiable only if actual advan- 
tages were obtained, which is not the case, because, though the 
platinum does absolutely not dissolve, the deficiency of metallic 
nickel in the bath caused by such anodes must be in some manner 
replaced. The insoluble anodes of gas-carbon which have fre- 
quently been proposed are attacked by the bath ; particles of car- 
bon becoming constantly detached, and floating upon the bath, 
deposit themselves upon the objects and cause the layer of nickel 
to peel off. Furthermore, by the use of nickel anodes in conjunc- 
tion with carbon anodes, the current, on account of the greater re- 
sistance of the latter, is forced to preferably take its course through 
the metallic anodes, in consequence of which the articles opposite 
the nickel anodes are more thickly nickelled than those under the 
influence of the carbon anodes. With larger objects this in- 
equality in the thickness of the deposit is again a hindrance to 



DEPOSITION OF NICKEL AND COBALT. 155 

obtaining layers of good and uniform thickness such as are re- 
quired for solid nickelling. According to long practical experi- 
ence, the best plan is to use rolled and cast anodes together in one 
bath. The proportion of cast to rolled anodes depends on the 
composition of the bath, but it may be laid down as a rule, that 
baths with greater resistance require more cast anodes, and baths 
with less resistance more rolled anodes. Cast anodes, to be sure, 
have the disadvantage of soon becoming spongy, and crumbling 
before being entirely used up. Furthermore, the surfaces of nickel 
anodes cast in 'iron moulds are so hard as to temporarily resist the 
action of the bath, while the interior dissolves only partially, since, 
on the one hand, the oxygen separating on the anode, which is 
necessary for solution, escapes partially unused, and on the other, 
the intact outer layer prevents the bath from coming in contact 
with the interior of the anode. 

The cast anodes suspended to the ends of the conducting rods 
are especially strongly attacked, and, therefore, when rolled and 
cast anodes are used together, it is best to suspend the latter more 
towards the centre, and the first on f the ends of the rods. 

These disadvantages, however, are not sufficient to prevent the 
use of a combination of cast and rolled anodes when required by 
the composition of the bath. The spongy remnants are thoroughly 
washed in hot water, dried and sold. 

The rolled nickel anodes are less liable to corrosion, and may be 
used up to the thickness of a sheet of paper before they fall to 
pieces. It is, however, best to replace them by fresh anodes be- 
fore they become too thin, since with the decrease in thickness 
their resistance increases. 

The surface of the anodes suspended in the baths should be at 
least as large as that of the articles to be nickelled ; it is however 
preferable that they should present twice or three times the sur- 
face, in order that the bath may be kept thoroughly saturated 
with nickel. 

It is best to allow the anodes to remain quietly in the bath, 
even when the latter is not in use, they being in this case not 
attacked. By frequently removing and replacing them they are 
subject to concussion, in consequence of which they crumble much 
more quickly than when remaining quietly in the bath. 



156 ELECTRO-DEPOSITION OF METALS. 

In the morning, before nickelling is commenced, the anodes will 
frequently show a reddish tinge, which is generally ascribed to a 
content of copper in the bath or in the anodes. This reddish 
coloration also appears when an analysis shows the anodes as 
well as the bath to be absolutely free from copper. It is very 
likely due to a small content of cobalt, from which nickel 
anodes can never be entirely freed. It would seem that by the 
action of a feeble current cobaltous hydrate is formed, which 
however immediately disappears on conducting a strong current 
through the bath. 

The anodes are supported by nickel wire 0.11 to 0.19 inch 
thick or by strips of nickel sheet riveted on. 

If after working for some time a nickel bath has become alka- 
line, which can he readily determined by testing with litmus-paper, 
its neutrality or a slightly acid reaction can be restored in a few 
minutes by the addition of either citric, sulphuric, acetic, or boric 
acid, according to the composition of the bath. On the other 
hand, when the bath contains too much free acid, it is removed 
by the addition of spirits of sal ammoniac, ammonium carbonate, 
potash, or by boiling with nickel carbonate, the choice of the 
remedy depending on the composition of the bath. 

The process of electro-nickelling. — Next to the correct composi- 
tion of the bath and the proper selection of the anodes, the suc- 
cess of the nickelling process depends on the thorough cleansing of 
the objects and the correct current-strength. 

The directions for the removal of grease, etc., given on p. 131, 
also apply to objects to be nickelled. In executing the manipula- 
tions, it should always be borne in mind that though dirty, greasy 
parts become coated with nickel, the deposit immediately peels 
off by polishing, because an intimate union of the deposit with 
the basis-metal is effected with only perfectly clean surfaces. 
Touching the cleansed articles with the dry hand must be strictly 
avoided ; but, if large and heavy objects have to be handled, the 
hands should first be freed from grease by brushing with lime 
and rinsing in water, and be kept wet. 

As previously mentioned, the cleansed objects must not be ex- 
posed to the air, but immediately placed in the bath, or, if this is 
not practicable, be kept under clean water. 



DEPOSITION OF NICKEL AND COBALT. 157 

While copper and its alloys (brass, bronze, tombac, German 
silver, etc.), as well as iron and steel, are directly nickelled, zinc, 
tin, Britannia, and lead are generally first coppered or brassed. 
With a suitable composition of the nickel bath and some experience, 
the last-mentioned metals may also be directly nickelled, but, as 
a rule, previous coppering or brassing is preferable, the certainty 
and beauty of the results being thereby considerably increased. 

Many operators prefer coppering or brassing steel and iron 
articles before nickelling, and claim that by so doing better pro- 
tection against rust is secured. While experiments have shown 
that with the thin coat of copper or brass generally applied this 
claim is scarcely tenable, the previous coppering of iron objects 
has the advantage that, in case they have not been thoroughly 
cleansed, the deposit of nickel is less liable to peel oif, the alka- 
line copper bath completing the removal of grease, but with 
objects carefully cleansed according to the directions given on p. 
126 previous coppering is not necessary. 

The objects should never be suspended in the bath without current, 
the baths, with few exceptions, exerting a chemical action upon 
many metals which is injurious to the electro-plating process, and 
especially with the nickel bath is it necessary to connect the anode- 
rods and object-rods before suspending the articles in the bath. 

The suitable current-strength has already been fully discussed on 
p. 76 et seq. (" Electro-plating Arrangements in Particular"), and 
referring the reader to that section we may here be comparatively 
brief. 

In that section it has been said that the surfaces of objects to be 
nickelled must be in due proportion to the effective zinc surface 
of the battery if the latter be used for generating the current ; 
further, the surface of anodes suspended in the bath must be at 
least equal to that of the objects, though in most cases it is better 
that it should be larger. On p. 1 7 et seq., it has also been ex- 
plained how, according to circumstances, the elements have to be 
coupled to a battery in order to be sure of success. Two Bunsen 
elements, coupled one after the other, yield for nearly all nickel 
baths the electro-motive force required for the reduction of the 
nickel ; for baths with great resistance it will, however, be better, 
especially when the filling of the elements is no longer fresh, to 



158 ELECTKO-DEPOSITION OF METALS. 

couple three elements one after the other, and to neutralize a 
momentary excess of current by the resistance board. 

An error is frequently committed in nickelling with too strong 
a current, the consequence being that the deposit on the lower 
portions of the objects soon becomes dull and gray-black, while 
the upper portions are not sufficiently nickelled. This phenome- 
non, which is due to the reduction of the nickel with a coarse 
grain in consequence of too powerful a current, is called burning 
or over-nickelling. A further consequence of nickelling with too 
strong a current is that the deposit readily peels off after it reaches 
a certain thickness. This phenomenon is due to the hydrogen 
being condensed and retained by the deposit, which is thereby 
prevented from acquiring greater thickness. 

Especially do those objects suspended on the ends of the rods 
nickel with great ease ; this evil can be avoided by hanging on 
both ends of the rods a strip of copper-sheet about 0.39 inch wide, 
and of a length corresponding to the depth of the bath. 

The following criteria may serve for judging whether the nickel- 
ling progresses with a correct current-strength : In two or at the 
utmost three minutes all portions of the objects must be percep- 
tibly coated with nickel, but without a violent evolution of gas 
on the objects ; small gas bubbles rising without violence and 
with a certain regularity are an indication of the operation pro- 
gressing regularly. If, after two or three minutes, the objects 
show no deposit, the current is too iveak, and in most cases the 
objects will have acquired dark, discolored tones. In such case 
either a stronger current must be introduced by means of the 
resistance board, or, if the entire volume of current generated 
already passes into the bath, the object-surface has to be dimin- 
ished, or, if this is not desired, the battery must be strengthened 
by adding more elements, or by fresh filling, etc. 

If, on the other hand, a violent evolution of gas appears on 
the objects, and the latter are well covered in a few seconds, and 
the at first white and lustrous nickelling changes in a few minutes 
to a dull gray, the current is too strong, and must be weakened 
either by the resistance board, or uncoupling a few elements, or 
diminishing the anode-surface, or finally by suspending more 
objects in the bath. 



DEPOSITION OF NICKEL AND COBALT. l59 

The density of current most suitable for nickelling copper, 
copper-alloys, iron, and steel varies between 0.4 and 0.8 ampere 
per 15.5 square inches, while zinc, after previous coppering, 
requires 1.3 to 1.5 amperes. 

It is in all respects advisable first to cover the objects by 
means of a strong current, i. e., to give the first deposit rapidly, in 
order to withdraw the metals from the action of the bath, and 
then finish the operation after reducing the current to a suitable 
strength. With a current thus regulated the objects may be 
allowed to remain in the bath for hours and even for days. It is 
further possible to nickel by weight and attain deposits of con- 
siderable thickness. 

If very thick deposits of nickel are desired, the objects must be 
frequently turned in the bath, as the lower portions nickel stronger 
than the upper ; further, as soon as the deposit acquires a dull 
bluish lustre it has to be thoroughly scratch-brushed, in doing 
which, however, the objects must not be allowed to become dry. 
After scratch-brushing it is advisable to cleanse the deposit once 
more with the lime-brush, and after rinsing replace the objects in 
the bath. If burnt places cannot be brightened and smoothed 
with the scratch-brush, the desh^ed end is readily attained with 
the assistance of emery paper or pumice. 

For solid nickelling it suffices in most cases to allow the objects 
to remain in the bath until the dull bluish lustre appears, this 
being an indication that the deposit has acquired considerable 
thickness, and will not take a further regular deposit. If such 
objects are permitted to remain longer in the bath without 
scratch-brushing, the dull bluish tone soon passes into a dull 
gray, and all the metal deposited in this form must be polished 
away in order to obtain a bright lustre. 

Whether the deposit of nickel is sufficiently heavy for all 
ordinary demands is, according to Fontaine, shown by rubbing a 
nickelled corner or edge of the object rapidly and with energetic 
pressure upon a piece of planed soft wood until it becomes hot. 
The nickelling should bear this friction. 

If the objects, after having been suspended for some time in 
the bath, are only partially nickelled, it is very likely due to the 
defective arrangement of the anodes. This occurs chiefly with 



160 ELECTRO-DEPOSITION OF METALS. 

large round objects and with articles having deep depressions 
(cups, vases, etc.). 

For flat objects it is sufficient to suspend them between two 
rows of anodes ; round objects with a large diameter should be 
quite surrounded with anodes, and be as nearly as possible equi- 
distant from them. This arrangement should especially not be 
neglected where a heavy and uniform deposit of nickel is to be 
given to round or half-round surfaces — for instance, large half- 
round stereotype plates for revolving presses. 

While for smooth articles the most suitable distance of the 
anodes from the objects is 3f to 5f inches, for objects with 
depressions and hollows it must be larger, if it is not preferred to 
make use of the methods described later on. However, a deposit 
of a uniform thickness cannot be obtained by this means, because 
the portions nearer to the anodes will acquire a thicker deposit 
than the hollows ; hence the use of a small hand anode, which is 
connected by means of a thin flexible wire with the anode-rod, 
and introduced into the depressions and hollows, is to be pre- 
ferred. This, of course, renders it necessary for a workman to 
stand alongside the bath and execute the operation by hand ; but 
as the small anode can be brought within a few millimetres of 
the surface of the article, and at this distance slowly moved 
around it, a correspondingly thick deposit is in a short time 
formed. 

In nickelling lamp-feet of cast-zinc this operation can hardly 
be avoided, especially if the depressed portions are also to have 
a uniformly good deposit. 

Besides the above-mentioned rules for nickelling, which also 
hold good for other electro-plating processes, the following may 
be given : — 

In suspending the objects in the bath rub the metallic hooks or 
wires, with which they are secured to the rods, a few times to and 
fro upon the rod, in order to be sure that the place of contact is 
purely metallic. It is also well to acquire the habit of striking 
the rod a gentle blow with the finger every time when suspending 
an object, the gas-bubbles settling on the articles becoming thereby 
detached and rising to the surface. It is further advisable, before 
securing the object to the object-rod, several times to move them 



DEPOSITION OF NICKEL AND COBALT. 161 

up and down ; so to say, shake them beneath the fluid, whereby, 
on the one hand, the layers poorer in metal are mixed with those 
richer in metal, and, on the other, any dust which may float upon 
the bath and settle on the objects is removed. 

The objects suspended in the bath should not touch one another, 
nor one surface cover another, and thus withdraw it from the 
direct action of the anode. In the first case stains will readily 
form on the places of contact, and in the latter the covered surface 
acquires only a slight deposit. That the objects must not touch 
the anodes need scarcely be mentioned. 

Objects with depressions and hollows should be suspended 
in the bath so that the air in the hollows can escape, which is 
effected by turning the depressions upward, or, if there are several 
depressions on opposite sides, by turning the articles about after 
being introduced into the bath. Air-bubbles remaining in the 
hollows prevent contact with the solution, no deposit being formed 
on such places. 

It remains to say a few words in regard to the so-called polar- 
izing phenomena. In the theoretical part, it has been shown that 
by dipping two plates of different metals in a fluid a counter or 
polarizing current is generated, which is the stronger the further the 
two metals are removed from one another in the series of electro- 
motive force, and the more they differ in their electrical behavior. 
If the anodes in a nickel bath are of nickel and the articles of cop- 
per, the counter-current will be slight, because copper and nickel 
stand together in the series of electro-motive force (p. 14). The 
counter-current, however, becomes greater when iron objects are 
hung in the bath, and greatest with zinc surfaces which are to be 
nickelled, because zinc, being the most electro-positive metal, dif- 
fers widely in its behavior from nickel. Now, since the counter- 
current flows in a direction opposite to that of the current intro- 
duced in the bath, the latter is weakened, and the more so the 
stronger the counter-current is. This explains why iron requires 
a stronger current for nickelling than copper alloys, and zinc a 
stronger one than iron. 

Now it may happen that the counter-current becomes so strong 
as to entirely annul the effect of the principal current, and even 
to reverse the latter, the consequence being that, in the first case, 
11 



162 ELECTRO-DEPOSITION OF METALS. 

the formation of the deposit is interrupted, and, in the latter, that 
the deposit is again destroyed, and the metals of which the articles 
consist dissolve and contaminate and spoil the bath. To avoid 
this, a main current must be conducted into the bath, Avhich, by 
its sufficiently large electro-motive force, can overcome the 
counter-current, and the consequences of the reversion of the 
current can be prevented by using the galvanometer and observ- 
ing the deflection of its needle, which (according to p. 86) in 
proper time indicates the appearance of a reversed current. Now 
if a nickel-plater has only a slight current at his disposal, it fol- 
lows from the above explanation that before nickelling the more 
electro-positive metals, such as iron, tin, zinc, it is best to first 
copper them, and thereby annul the action of these metallic sur- 
faces as regards the formation of the counter-current. 

It happens comparatively seldom that the counter-current 
becomes so strong as to destroy the deposits formed, because for 
nickelling powerful Bunsen elements, with two acids or dynamo- 
electric machines with at least 4 volts' tension, are generally used ; 
it is, however, well to acquaint the operator with all possible con- 
tingencies, and to explain the reason why the articles are prefer- 
ably covered with a strong current. Sprague recommends an 
initial current of 5 volts' tension, but in most cases one of 3.5 
volts suffices for nickelling iron and copper alloys. 

Nickelling en masse of small and cheap objects. — This is effected 
by stringing the objects, if feasible, upon a copper wire, and 
placing a large glass bead between every two objects to prevent the 
surfaces from sticking together in the bath. Such objects being 
generally only slightly nickelled, it suffices to allow them to re- 
main for a few minutes only in the bath with a strong current, it 
being advisable to diligently shake the bundles in order to 
effect a change of position of the objects and prevent their 
touching one another, notwithstanding the glass bead placed 
between them. 

Very small objects which cannot be strung upon wire are 
nickelled in sieves. To the bottom of a stoneware sieve is secured 
a copper or brass wire, which is connected with the object-rod, 
and then the objects are placed in the sieve. Since nickel baths, 
as a rule, do not conduct sufficiently well to nickel the objects in 



DEPOSITION OF NICKEL AND COBALT. 



163 



the sieve, which must be constantly shaken, it is advisable to 
hold with one hand an anode connected by a flexible wire with 
the anode-rod in the sieve, while the other holds the sieve 
(Fig. 100) and constantly shakes and turns it. For nickelling 
in sieves, it is further advisable to heat the nickel bath. 

Fig. 100. 




Warren has recently described a solution of nickel and one of 
cobalt which can be decomposed in a simple cell apparatus. 
With the nickel solution, which was prepared by dissolving 100 
parts by weight of nickel chloride in as little water as possible 
and mixing with a concentrated solution of 500 parts of Eochelle 
salt, no satisfactory results could be obtained ; the cobalt solution 
however yielded good results, and would seem to be suitable for 
electro-plating small objects en masse. It will be further dis- 
cussed under " Cobalting." 

Stripping nickelled articles. — Defective or old nickelling has 
first to be removed before the objects can be re-nickelled, since 
nickel will not adhere to a coating of the same metal. Only in 
a few isolated cases can stripping be effected by grinding the 
article. The following process, which is applicable to all metals, 
but especially to iron, may be recommended. It is based on the 



164 ELECTRO- DEPOSITION OF METALS. 

property of concentrated nitric acid to dissolve nickel, but not 
iron. The surface of the latter is changed by the nitric acid in 
such a manner as to protect it from the further action of the 
acid, a thin film of magnetic oxide of iron being formed. Iron 
in this state is designated passive. The articles to be treated are 
first freed from adhering fat by washing in a soap bath or in a 
solution of caustic soda, or by means of benzine. The rust is 
next removed, which is best effected by connecting the article 
with a piece of sheet-zinc and placing it in a mixture of 100 
parts water and 1 part sulphuric acid until the rust spots have 
disappeared, or can at least be readily removed by wiping. The 
article is then dried and treated in the nitric acid bath. For the 
latter it is best to use a mixture of 1 part by volume of nitric 
acid and 10 parts by volume of sulphuric acid of QQ° B. The 
acid mixture should be kept in a vessel of glass, porcelain, or 
stoneware, or in a wooden trough lined with lead, and when not 
in use should be covered. The articles to be stripped are placed 
in the acid bath and allowed to remain until the nickelling; is 
completely dissolved. Should this not be the case in the course 
of one hour, the articles are taken from the bath by means of an 
iron tool, rinsed quickly in running water to dissolve and remove 
the nickel salts not soluble in the acid, and dried with cloths. 
They are then replaced in the acid. When the nickelling is 
entirely dissolved, the articles are rinsed in water and brought 
immediately into the nickel bath, or if they are to be coppered 
before nickelling, as is frequently done, into a cyanide of copper 
bath. Iron and steel treated with the above-described acid mix- 
ture show, in the passive state, no tendency to the formation of 
rust, and it might, therefore, be advisable in all cases to pickle 
articles of iron and steel, which are to be nickelled, in a mix- 
ture of nitric and sulphuric acids, after freeing them from fat, in 
order to counteract the rust spots which frequently show them- 
selves later on, especially in cast-iron. The durability of the 
nickelling seems not to be affected by the layer of magnetic oxide 
of iron. Should its removal, however, be deemed desirable, it 
can be readily effected by connecting the article with a piece of 
sheet zinc and immersing it in dilute sulphuric acid. Articles of 
copper, brass, or zinc may also be stripped by immersing them in 



DEPOSITION OF NICKEL AND COBALT. 165 

the above-mentioned acid bath. After being placed in the strip- 
ping bath they should be carefully watched, being frequently 
taken from the bath to see how the operation progresses, and they 
should not be allowed to remain in the liquid one moment after 
the nickel has been dissolved from the surface. The operation of 
stripping should be conducted in the open air, or in a fireplace 
with good draught, so that the acid fumes may escape through 
the chimney. When the stripping of brass or copper work has 
been properly conducted, the surface of the stripped object pre- 
sents a smooth and bright surface but little affected by the acid 
bath. 

The old nickelling is removed mechanically by brushing with 
emery. From depressions as much as possible is removed with 
the brush, after which the object is freed from grease and pickled 
and coppered before nickelling. In this case the layer of copper 
serves as a cement for the old and new deposit, and there will be 
no danger of the new deposit peeling off in polishing. 

It has also been proposed to remove the nickel from the articles 
by means of the battery or dynamo-machine by making them the 
anodes in a nickel bath ; but in this case a separate solution should 
be employed for the purpose. 

As a remedy against the yellowish tone of the nickelling, Pfan- 
hauser recommends suspending the nickelled articles, immediately 
after taking them from the nickel bath, as anodes in a nickel bath 
acidulated with citric or hydrochloric acid, a piece of sheet nickel 
serving as the cathode, and to allow the current to act for a few 
seconds. It is claimed that thereby the basic nickel salts sepa- 
rated together with the nickel, and to which, according to Pfan^ 
hauser, the yellowish tinge is due, are dissolved and the nickelling 
will show a pure white tone. 

The following is a brief compilation of the principal pheno- 
mena which may occur in nickelling, as well as the means of 
avoiding them : 1. The articles do not become coated with 
nickel, but acquire discolored, generally darker tones. Rea- 
sons: The current is either too feeble to effect the reduction of 
nickel, and the coloration is in consequence of the chemical action 
of the nickel solution upon the metals constituting the objects. 
Remedy : Increase the current or diminish the area of suspended 



166 ELECTRO-DEPOSITION OF METALS. 

objects; also examine whether the current actually passes into the 
bath, otherwise clean the places of contact. 

2. A deposition of nickel takes place, but it is dark or spotted 
or marbled, even with a sufficiently strong current. Reasons: 
The bath is either alkaline, which has to be ascertained by litmus- 
paper, and, if so, the slightly acid reaction of the bath has to be 
restored by the addition of a suitable acid ; or, the bath is too 
concentrated, in which case a separation of crystals will be ob- 
served. This is remedied by diluting with water ; or, the nickel 
solution is very poor in metal, which can be remedied by the ad- 
dition of nickel salt ; it should also be tested as to the admixture 
of copper, the production of dark tones being frequently due to 
this. In this case the bath is allowed to work for some time, and 
if the content of copper is inconsiderable a white deposit will 
soon be obtained ; or, the cleaning and pickling of the articles have 
not been thoroughly done, which is remedied by again cleaning 
them ; or, the conducting power of the bath is insufficient, which 
is remedied by the addition of a suitable conducting salt. 

When freshly prepared baths yield dark nickelling, it can gen- 
erally be remedied by working the bath two or three hours. 

3. A yellowish tinge of the nickelling. Reasons : See under 
2; or, with cast-iron an insufficient metallic surface, which is 
remedied by repeating the scratch-brushing ; or, unsuitable com- 
position of the bath. 

4. The objects rapidly acquire a white deposit of nickel, but 
the color soon changes to dull gray-black, especially on the lower 
edges and corners. Reason: Too strong a current. Remedies: 
Regulating the current, or hanging in more objects, or uncoupling 
elements. Frequent turning of the articles. 

5. The nickelling is white, but readily peels off by scratching 
with the finger-nail or by the action of the polishing wheel. 
Reasons: The current is too strong, which is remedied as under 
4 ; or, the bath is too acid. This is remedied by the addition of 
spirit of sal ammoniac, potassium carbonate, or nickel carbonate, 
according to the composition of the bath : or, insufficient cleaning 
and pickling, which is remedied by thorough cleaning after re- 
moving the defective deposit, or, if it cannot be entirely removed, 
coppering. 



DEPOSITION OF NICKEL AND COEALT. 167 

6. Though nickelling may proceed in a regular manner, some 
places remain free from deposit. Reasons: Either the surfaces 
of some of the objects touch one another, or air bubbles are in- 
closed in cavities ; or, faulty arrangement of the anodes. Remedy : 
Removal of the causes. 

7. The deposit appears with small holes. Reason : A deposit 
of particles of dust upon the objects. Remedy : Remove the dust 
from the surface. When there is a general turbidity of the bath 
in consequence of alkalinity, add the most suitable acid, and boil 
and filter the bath ; or, insufficient removal of gas bubbles from 
the objects. Remedy: Shake the object-rods by blows with the 
finger. 

8. Deposition takes place promptly upon the portions of the 
objects next to the anodes, while deeper portions remain free from 
nickel or become black • or the portions covered by the suspend- 
ing ware show dark lines. Reason: Insufficient conducting 
power of the bath. With large depressions this cannot be reme- 
died by the addition of a suitable conducting salt, but requires 
treatment with the hand-anode. 

Refreshing nickel baths. — According to their composition, the 
amount of work performed, and the anodes used, the baths will 
in a shorter or longer time require certain additions in order to 
keep their action constant. By " refreshing" is not understood 
the email addition of acid or alkali from time to time required for 
restoring the original reaction of the baths, but additions intended 
to increase the metallic content and diminished conductivity. 

The metallic content is increased by boiling the bath with some 
of the nickel salt used in its preparation, while the conductivity 
is improved by adding, at the same time, so much conducting salt 
as is necessary to restore the electro-motive force originally re- 
quired, Nothing definite can, of course, be said in regard to the 
quantity of such additions, it being advisable to observe their 
effect on a small portion of the bath, so as to be sure not to spoil 
the entire bath, „ 

Nickel baths bear, as a rule, refreshing several times, but as in 
the course of time they take up impurities, even when the greatest 
care is exercised, it is best to refresh them at the utmost twice, 
arid then to renew them entirely, 



168 ELECTRO-DEPOSITION OF METALS. 

Nickel deposits are polished upon felt disks or bobs of cloth, 
muslin, or flannel, with the use of Vienna lime, rouge, etc. (See 
" Polishing," page 116.) Sharp edges, corners, and raised portions 
should be held only with slight pressure against the polishing 
wheels, they being more strongly attacked by them than flat sur- 
faces. Knife-blades and surgical instruments with sharp edges 
require special care in polishing, which will be referred to later on. 

After polishing, the nickelled objects, especially those with de- 
pressions, have to be freed from polishing dirt by brushing with 
hot soap-water or hot caustic lye, then rinsed in hot water and 
dried in clean, fine sawdust. 

Objects which are not required to be polished, but left dead, 
that is, just as they come out of the nickel bath, should be taken 
from the bath one at a time, and at once plunged into perfectly 
clean hot water for a few moments, and then placed aside to dry 
spontaneously. Dead nickel being very readily stained or soiled, 
even when touched with clean hands, the work should be handled 
as little as possible. 

Nickelling sheet zinc- — The nickelling of sheet zinc has been 
surrounded with a great deal of mystery by those engaged in its 
manufacture, which may, perhaps, be excusable on the ground 
that there is scarcely another branch of the electro-plating indus- 
try in which experience had to be acquired at the sacrifice of so 
much money and time as in this. Nevertheless the nickelling of 
sheet zinc makes no greater demand on the intelligence of the 
operator than any other electro-plating process, it requiring only 
an accurate consideration of the relations of the electric behavior 
of zinc towards nickel ; consequently, a knowledge of the strength 
of the counter-current and of the chemical behavior of zinc 
towards the nickel solution, which may readily dissolve the zinc; 
further, a correct estimation of the current-intensity required for 
a determined zinc surface, as well as of the proper anode-surface, 
and the most suitable composition and treatment of the nickel baths. 

With due observation of these relations, the nickelling of sheet 
zinc is accomplished as readily as that of other metals ; and the 
proposals to first cover the sheets in a bath with a strong current, 
and finish nickelling with a weaker current, or to amalgamate the 
zinc before nickelling, need not be considered. 



DEPOSITION OF NICKEL AND COBALT. 



169 



Below the conditions required for nickelling sheet zinc, and the 
execution of the process itself, together with the preliminary and 
final polishing of the sheets, will be fully described. 

The preliminary grinding or polishing is effected upon broad 
cloth disks (buffs) formed of separate pieces of cloth. The polish- 
ing lathes run with their points in movable bearings secured in a 
hanging cast-iron frame by a set screw and safety keys, or pre- 
ferably as shown in Fig. 86, p. 118, since with this construction 
an injury to the grinder by the lathe jumping out is impossible. 

The buffs, when new, have on an average a diameter of 12 to 
16 inches, and a width of 5f to 8 inches ; the principal point in 
the construction of these bobs is uniform weight on all sides, the 
quiet running and the possibility of a good polish without great 
exertion depending on this. Bobs not well balanced run unsteadily 
and jump, thereby producing fine scratches upon the sheet. The 
bobs are constructed as follows : A square piece of cloth is folded 
fourfold and the closed point cut off with a pair of scissors, so 
that on unfolding the cloth the hole produced by the cut is exactly 
in the centre of the cloth disk ; according to the diameter of the 
spindle more or less is cut away, but in every case just sufficient 
that the piece of cloth can be conveniently pushed upon the 
spindle. The latter, which is provided with a pulley and a hoop 
against which the pieces of cloth fix themselves, as well as with a 
nut and screw for securing them, is vertically fastened in a vise, and 
the separate pieces of cloth are pushed upon it so that the second 
piece placed in position forms an angle of about 30° (Fig. 101) 
with the first, the operation being thus con- 
tinued until the bob has the desired width. 
Next a small, but very strong iron disk is 
laid upon the cloth disk, and the separate 
pieces are pressed together as firmly as pos- 
sible with the screw. The spindle is then 
placed in the bearings, and after adjusting 
the belt upon the pulley the bob is revolved, 
a sharp knife being held against it to re- 
move the projecting corners. In polishing 

sheet zinc the bobs make 2400 to 3000 revolutions per minute, ac- 
cording to whether finely rolled or rougher sheets are to be polished. 




170 ELECTEO-DEPOSITION OF METALS. 

For the purpose of polishing or grinding, the operator places 
the sheet upon a support of hard wood of the same size and form 
as the sheet, and grasps the two corners of the sheet nearest to his 
body, together with the support, with the hands, applying with 
the balls of the hands the necessary pressure to hold the sheet 
upon the support. The lower half of the sheet, that furthest 
from the body, rests upon the knees of the operator, and with them 
he presses the sheet against the polishing disk, constantly moving 
at the same time, and at not too slow a rate, the knees from the right 
to the left, then from the left to the right, and so on. Previous to 
polishing a streak of oil about 2 inches wide is applied by means 
of a brush to the centre of the sheet in the visual line of the 
operator, and the revolving bob is impregnated with Vienna 
lime by holding a large piece of it against it, when polishing 
of the lower portion of the sheet begins. When about §- of 
the surface has thus been polished, the sheet is turned round and 
the remaining portion subjected to the same process. The sheet 
is then closely inspected to see whether there are still dirty or 
dull places, and, if such be the case, it is polished once more after 
moistening it with some oil and again impregnating the bob with 
Vienna lime. The sheet being sufficiently polished, the oil and 
polishing dirt are removed by dry polishing, after providing the 
bob with sufficient Vienna lime, so that the sheets when finished 
show no streaks of dirt or oil. 

Self-acting sheet polishing machines have been constructed by 
Dr. Sackur, F. Rauber, Eliachoff, and others. Such machines 
give a very good polish, but have the disadvantage that thin 
sheets when polished upon them become wrinkled or wind up 
on the polishing roller. 

In order to explain the principle upon which these machines 
are constructed, a description of F. RMuber's sheet grinding and 
polishing machine is given. With this machine metallic sheets of 
any length can be polished ; by the simultaneous lateral and 
longitudinal motion of the sheet a faultless polish is obtained, 
streaks and scratches being especially avoided. 

The machine essentially consists of the gearing A and the 
actual polishing machine B, Figs. 102, 103, 104. The gearing 
A consists of the two standards a a, the shaft b } a fast and loose 



DEPOSITION OF NICKEL AND COBALT. 



171 



pulley, c c, the large driving-wheel d, a small-driving wheel, e, 
and the eccentric/. 



Fig. 102. 




The polishing machine B consists of the wooden frame g with 
wooden plate h, the two standards i i, the polishing roller k, the 
iron counter-roller I, the expanding contrivance m, which is 
effected by means of three spiral springs, the gearing n with the 
rope-drum o, the rope with the tongs g, and the shaking arrange- 
ment x. 

The machine is set in motion by the engaging coupling x on 
the gearing A. The shaft of the gearing makes about 200 revo- 
lutions per minute, and the polishing roller k is revolved by a 
belt from the driving-wheel d. At the same time the gearing n 
is set in motion by a belt from the driving-wheel e, in consequence 
of which the rope is wound upon the drum o, and the tongs on 
the rope draw the sheet to be polished under the polishing roller. 
If the sheet is to go back, the rope-drum o is disengaged by 
means of the coupling y, and the polishing roller k } which moves 
lightly upon the counter-roller I, draws the sheet back. To pre- 
vent the sheet from jumping back, the brake r is provided on the 
rope-drum o. By the treadle r x the workman is enabled to trans- 
port the sheet slowly or rapidly, as may be required. To move 
the sheet forward, the rope-drum o is again engaged. The lateral 
motion of the sheet is effected by the shaking contrivance x. 

From the eccentric/, of the gearing A, the slide rod t is con- 



172 



ELECTRO-DEPOSITION OF METALS. 




nected with the joint lever x and the latter by the pin s with the 
table plate h, whereby the latter when the machine is running is 
moved to the sides. 

The centre of motion of the table plate is upon the pin v. To 
regulate the pressure of the sheet against the polishing roller, the 



DEPOSITION OF NICKEL AND COBALT. 173 

expanding arrangement m is placed under the table plate h. It 
consists of three vertical bolts with spiral springs, each of which 
can be screwed up and down by a nut. 

To facilitate the lateral motion of the table plate h, the bolts of 
the expanding contrivance ra are provided with rolls which press 
against the plate. If the tension is sufficient and a sheet is to be 
introduced, it is only necessary to draw the table plate down by 
means of the treadle w, to push the sheet under the polishing roll 
k, and to engage the tongs g. In front of the gearing A is a table 
for the reception of the sheet, as shown in the illustration. 

The sheets are best freed from grease in two operations, first 
dry and then wet. For the dry process use a very soft piece of 
cloth, and, after dipping it in Vienna lime very finely pulverized 
and passed through a hair sieve, rub over the sheet in the direction 
at a right angle to the polishing streaks, applying a very gentle 
pressure. For the wet process dip a wet piece of cloth or a soft 
sponge free from sand into a paste of impalpable Vienna lime, 
whiting, and water, and go carefully over the sheet so that no 
place remains untouched. Then rinse the sheet under a powerful 
jet of water, best under a rose, being especially careful to remove 
all the lime, going over the sheet, if necessary, with a soft wet rag 
and observing whether all portions appear evenly moistened. If 
such be the case, the cleaning is complete, otherwise the sheet has 
to be treated once more with lime. 

If the sheets are to be nickelled on only one side, two of them 
are placed together with their unpolished sides and fastened on 
the two upper corners with binding screws to which is soldered a 
copper strip about 0.39 inch wide, by which they are suspended 
to the conducting rods. Plating is then at once proceeded with 
without allowing the sheets to remain exposed to the air longer 
than is absolutely necessary. Special care must be had that the 
lime does not dry, as this would produce stains. 

Some manufacturers nickel the cleansed sheets without previous 
coppering or brassing, and claim special advantages for such direct 
nickelling. This may be done with a bath of nickel sulphate and 
potassium citrate without or with a greater or smaller addition of 
sal ammoniac, according to the area to be nickelled and the inten- 
sity of current at disposal. However ; sheet zinc directly nickelled 



174 ELECTRO-DEPOSITION OF METALS. 

does not shows the warm full tone of sheets previously coppered 
or brassed ; besides, direct nickelling requires a far more powerful 
current, so that it is not even more economical. 

For the nickelling process itself, it is indifferent whether the 
sheets are previously coppered or brassed, but the choice between 
the two is controlled by a few phenomena which must be men- 
tioned. The nickel deposit upon brassed sheets shows a decidedly 
whiter tone than that upon coppered sheets, and brassing would 
deserve the preference if this process did not require extraordi- 
narily great care in the proper treatment of the bath, the nickel 
deposit readily peeling off generally in the bath itself, which 
seldom or never occurs with coppered sheet, and then may gene- 
rally be considered due to insufficient cleaning or other defective 
manipulation. 

This peeling off of the nickel deposit may be prevented by 
giving due consideration to the conditions, and avoiding, on the 
one hand, too large an excess of potassium cyanide in the brass 
bath, and, on the other, by regulating the current so that no pale 
yellow or greenish brass is precipitated. Since nickelling with a 
strong current requires only a few minutes for a deposit of suffi- 
cient thickness capable of bearing polishing, it is generally desired 
to brass the sheets at the same time, so that the operation may 
proceed rapidly and continuously. To do this, a very powerful 
current has to be conducted into the brass bath, the result being 
that a deposit with a larger content of zinc and a correspondingly 
lighter color is formed, but also with a coarser, less adherent 
structure, and this is the principal reason why the nickel deposit, 
together with the brass deposit, peels off. To avoid this, the 
brassing must be done with a current so regulated that the deposit 
separates uniformly, adheres firmly, and is not porous, the correct 
progress of the operation being recognized by the color being 
more like tombac, and not pale yellow or ' greenish. Where 
brassing has to be done quickly the content of copper in the brass 
bath must be increased to such an extent that a powerful current 
produces a deposit of the above-mentioned color, and, hence, too 
large an excess of potassium cyanide must be strictly avoided. 

It will be seen that the brassing requires a certain attention 



DEPOSITION OF NICKEL AND COBALT. 175 

which is not necessary in coppering, and therefore the latter is to 
be preferred. 

For coppering, one of the baths, III. or V., given under " Cop- 
pering" serves, to which, for this special purpose, more potas- 
sium cyanide may be added. The sheets should remain in this 
bath no longer than required to uniformly coat them with a 
beautiful red layer of copper, and under no circumstances must 
they be allowed to remain until the coppering commences to be- 
come dull or even discolored; and they should come from the bath 
with a full or at least half lustre. When taken from the copper 
bath the sheets are thoroughly rinsed in a large water reservoir, 
the contents of which must be frequently renewed, care being 
had to remove any copper solution adhering to the unpolished 
sides which are not to be nickelled, since that would soon spoil 
the nickel bath. The sheets are then immediately brought into 
the nickel bath, it being best to suspend two, three, or four plates 
at the same time, to prevent one from being more thickly nickelled 
than the other, and take them out the same way. In suspending 
the plates in the bath care should be had to bring them as soon 
as possible in contact with the conducting rod, a neglect of this 
rule being apt to produce blackish streaks and stains. 

Every separate nickel bath in which sheets are to be nickelled 
must be fed with the full current of a dynamo-machine, one of 
250 to 300 amperes with 4 volts' tension being generally used. 
According to the number of sheets, generally 6 to 8, each 20 x 20 
inches, to be nickelled, the dimensions of the vats are as follows : 
63 inches long, 15| inches wide, and 25| inches deep, or, 83 
inches long, 15f inches wide, and 25 J inches deep. One to two 
minutes suffice to give 6 sheets a sufficiently thick deposit of 
nickel with a dynamo-machine of the above-mentioned capacity, 
and 2 to 3 minutes for eight sheets, and it may be accepted as a 
rule that, with a bath of good conductivity, a density of current 
of from 1.4 to 1.5 amperes and 5 volts' tension is required per 
15.5 square inches of zinc surface for the solid nickelling of the 
sheets. For nickelling zinc in baths conducting with difficulty, 
for instance, a simple solution of sulphate of nickel and ammonia 
without the addition of conducting salts, or in baths containing 
boric acid, 1.3 to 1.4 amperes and 6 to 7 volts must be allowed 



176 ELECTRO-DEPOSITION OF METALS. 

per 15.5 square inches of zinc surface if the nickelling is to be 
effected in the above-named space of time. A density of current 
of 1.4 to 1.5 amperes and 4 to 4 J volts, at which the sheets have 
to remain in the bath for 3 minutes, is the most suitable, the de- 
posit thus obtained being in every respect faultless, provided the 
nickel bath is of proper composition. 

For nickelling sheet zinc rolled anodes are, as a rule, only used, 
except when working with baths containing boric acid. The 
anode surface must at least be equal to that of the zinc surface ; 
the distance between the anodes and the sheets should be from 3 
to 3f inches, and when the current-strength is somewhat scant 
the distance may be reduced to 2| inches. The nickel anodes 
have to be taken from the bath once daily and scoured bright 
with scratch-brushes and sand ; for the rest, all the rules given for 
nickel anodes are valid. 

Baths used for nickelling sheet zinc soon become alkaline in 
consequence of the powerful current used, which is shown by red 
litmus-paper turning blue ; the alkalinity also manifests itself by 
the bath becoming turbid and the nickelling not turning out a 
pure white. The slightly acid reaction is restored by citric acid 
solution. The appearance of the dreaded black streaks and stains 
is due either to the current itself being too weak or to its having 
been weakened by an extremely great resistance of the nickel 
bath ; also to an insufficient metallic surface of the anodes, which 
may be either too small or not sufficiently metallic on account of 
tarnishing ; and finally to an excessive alkalinity of the bath or 
insufficient contact of the hooks with the connecting rods. 

The metallic content of the bath must from time to time be 
augmented by the addition of nickel salt, and the bath filtered 
at certain intervals. When the conductivity abates it has to be 
be restored by the addition of conducting-salt. 

When the sheets have been sufficiently nickelled, they are 
allowed to drain off, then plunged into hot water, and, after re- 
moving the binding-screws, dried by gentle rubbing with fine 
sawdust free from sand and passed through a fine sieve to 
separate pieces of wood. In all manipulations, the unnickelled 
sides are placed together, while a piece of paper of the size and 
form of the sheets is laid between the nickelled sides. 



DEPOSITION OF NICKEL AND COBALT. 177 

The nickelled sheets are finally polished, which is effected by 
placing them upon supports and pressing against the revolving 
bob as previously described, the sheets being, however, only mode- 
rately moistened with oil, and not too much Vienna lime applied 
to the bob. Polishing is done first in one direction and then in 
another, at a right angle to this first. After polishing, the sheets 
are finally cleansed with a piece of soft cloth and impalpable 
Vienna lime, after which they should show a pure white lus- 
trous nickelling, free from cracks and stains, and bear bending 
and rebending several times without the nickelled deposit break- 
ing or peeling off. 

Nickelling of tin plate. — For elegant and durable nickelling tin 
plate also requires previous coppering. The deposit is effected 
with a less powerful current than is used for sheet zinc. Scour- 
ing is done as described for sheet zinc, also the polishing of the 
nickelled tin plate. 

The treatment of copper and brass sheets differs from that of 
sheet zinc in that the rough sheets are first brushed with emery 
and then polished with the bob. After treating the sheets with 
hot caustic lye or lime-paste, they are pickled by brushing them 
over with a solution of 1 part of potassium cyanide in 20 of 
water ; they are then thoroughly and quickly rinsed, and imme- 
diately brought into the bath. To avoid peeling off, the current 
must not be too strong. 

Nickelling of sheet-iron and sheet-steel. — Only the best quality 
of sheet should be used for this purpose. After rolling, the sheets 
are freed from scales by pickling, then passed through the fine 
rolls, and finally again pickled. If the nickelled sheets are not 
to exhibit a high degree of polish, it suffices to brush them before 
nickelling with a large broad fibre brush (p. 115) and emery No. 
00. But for a high lustre, such as is generally demanded, the 
sheets have first to be ground. For fine grinding the pickled 
sheets broad massive cylinders of poplar wood are used, which 
are covered with leather and turned like the disks described on p. 
112. These cylinders are 10 to 12 inches in diameter, and 2 to 4 
or more inches long, according to the size of the sheets. For the 
first grinding, the cylinders are coated with glue and rolled in 
emery No. 100 to 120, according to the condition of the sheets, 
12 



17S ELECTKO-DEPOSITION OF METALS. 

while emery No. 00 is applied to the cylinders used for fine grind- 
ing. The grinding is succeeded by brushing, as described on 
p. 112. 

After preparing a sufficiently smooth surface, the sheets are at 
once rubbed with a rag moistened with petroleum, or, if preferred, 
with a rag and pulverized Vienna lime ; they are then scoured 
wet in the manner described for sheet-zinc, p. 173. The scouring 
material must be liberally applied, especially if the sheets are to 
be directly nickelled without previous coppering, as is advisable. 
After rinsing off the lime-paste, the sheets are brushed over with 
very dilute sulphuric acid (1 part acid to 25 water), rinsed off, 
then lightly brushed over once more with lime-paste, again care- 
fully rinsed, and immediately brought into the nickel bath. 

The current should be neither too strong nor too weak, but 
regulated so that the nickelling is of sufficient thickness in 15 to 
20 minutes without showing a tendency to peel off. It is not 
advisable to try to obtain a heavy deposit in a shorter time, 
because it would lack density, which is the principal requirement 
for nickelled sheet-iron. 

After nickelling, the sheets are rinsed in clean water, then 
plunged into hot water and dried by rubbing with warm saw- 
dust. After this operation, it is recommended to thoroughly dry 
the sheets in an oven heated to between 176° and 212° F., to 
expel any moisture from the pores, and then to polish them with 
Vienna lime and oil or with rouge. 

Nickelling ofivire. — Nickelling of wire of iron, brass, or copper 
is scarcely ever done on a large scale ; it is, however, believed that 
the nickelling of iron and steel wires — for instance, piano-strings — 
might be of advantage to prevent rust or at least to retard the 
commencement of oxidation as long as possible. 

To nickel single wires cut into determined lengths, according 
to the general rules already given, is simple enough ; but this 
method cannot be pursued with wire several hundred yards long, 
rolled in coils, as it occurs in commerce. Nickelling the wire in 
coils, however, cannot be done, as only the upper windings exposed 
to the anodes would acquire a coat of nickel. Hence it becomes 
necessary to unwind the coil, and for continuous working pass the 



DEPOSITION OF NICKEL AND COBALT. 



179 



wire at a slow rate through the cleansing and pickling baths, as 
well as the nickel bath and hot water reservoir, as shown in Fig. 
105 in cross-section, and in Fig. 106 in ground plan. 




**, 






<a> mil 



■fr 






to «■ 



«*■?*& 




The unwinding of the wire is effected by a slowly revolving 
shaft, upon which the nickelled wire again coils itself ; but in the 



180 ELECTKO-DEPOSITTON OF METALS. 

illustration the shaft is omitted. In Fig. 105 four wires run over 
the four rolls a, mounted upon a common shaft, to the rolls b 
upon the bottom of the vat A, whereby they come in contact 
with a thickly fluid lime-paste in the vat, and are freed from 
grease. From the rolls b the wires run through the wooden 
cheeks i, lined with felt, which retain the excess of lime-paste, 
and allow it to fall back into the vat. The wires then pass over 
the roll c to the roll d. Between these two rolls is the rose g, 
which throws a strong jet of water upon the wires, thereby freeing 
them from adhering lime-paste. The roll d, as well as its axis, is 
of brass, and to the latter is connected the negative pole of the 
battery or dynamo, so that by carrying the wires over the roll d 
negative electricity is conducted to them. From the roll d the 
wires run over the roll-bench s (Fig. 105) to the vat C, which 
contains the nickel solution, so that they are subjected to the 
action of the anodes arranged in this vat on both sides of the 
wires. The wires then pass over the roll e, are rinsed under the 
rose s, and run finally through a hot water reservoir and sawdust 
(these two apparatuses are not shown in the illustration), to be 
again wound into coils. In case a high polish is required, the 
nickel led wires may be run under pressure through leather cheeks 
dusted with Vienna lime. 

Nickelling wire-gauze. — Messrs. Louis Lang & Son obtained, in 
1881, a patent for a method of nickelling wire gauze, or wire to 
be woven into gauze, more especially for the purpose of paper 
manufacture. These wires, which are generally of copper or brass, 
are liable to be attacked by the small quantities of chlorine which 
generally remain in the paper pulp, by which the gauze wire 
eventually suffers injury. To nickel wire before it is woven, it is 
wound on a bobbin and immersed in a nickel bath, in which it is 
coated with nickel in the usual way ; it is then unwound and re- 
wound on to another bobbin, and reimmersed in a nickel bath, as 
before, so as to coat such surfaces as were in contact with each 
other and with the first bobbin. To deposit nickel on the woven 
tissue it may either be coated in its entire length, as it leaves the 
loom, or in detached pieces. For this purpose the wire gauze is 
first immersed in a pickle bath, and next in the nickel solution. 
On leaving the latter it is rinsed and then placed in a hot air 



DEPOSITION OF NICKEL, AND COBALT. 181 

chamber, and when thoroughly dry may be rolled up again ready 
for use. 

Nickelling of knife-blades, sharp surgical instruments, etc. — Most 
electro-platers experience considerable trouble in nickelling sharp- 
edged instruments, the edges and points being invariably spoiled 
either by the deposit of nickel or in polishing. The following 
directions for the convenient nickelling of such instruments with- 
out any damage being done to the edges, are given by the Metal- 
arbeiter, and can be recommended : New articles which have 
not been used require no special preparation, they being at once 
freed from grease and brought into the bath. But instruments 
which have been used, and are partly or entirely coated with rust, 
must first be ground after the removal of the rust by chemical or 
mechanical means. The marks left by the stone or emery wheel 
are effaced by means of the circular brush. But in brushing, the 
edges are rendered dull if special precautionary measures are not 
used. For instance, the edge of a knife-blade must never come 
in contact with the brush. This is prevented by firmly pressing 
the blade flat upon a soft support of felt or cloth, so that the edge 
sinks somewhat into the support, without, however, cutting into 
it. The edge is then held downward and thus together with the 
support brought against the revolving brush. In this manner 
the blades may be vigorously brushed without fear of spoiling 
the edges. 

The treatment in giving them a high polish after nickelling is 
the same. Freeing from grease may be done in the usual manner 
with lime-paste; but must also be effected upon a soft support, 
the same as in polishing. After thorough rinsing in clean water 
the separate pieces, without being previously coppered, are brought 
directly into the nickel bath, the composition of which must, of 
course, be suitable for nickelling steel articles. The instruments 
are first coated with the use of a strong current, so that the depo- 
sition takes place slowly and with great uniformity. 

In suspending the articles in the bath, care should be had that 
neither a point nor an edge is turned towards the anodes. It is 
best to use a bath with anodes on one side only, and to suspend 
the blades with their backs towards the anodes. If, for any rea- 
son, the instruments are to be suspended between two rows of an- 



182 ELECTRO-DEPOSITION OF METALS. 

odes, the edges should be uppermost, as near as possible, to the 
level of the bath ; but they should never hang deep or downwards. 

After nickelling the instruments are polished for high lustre, but 
must always be exposed upon a soft support, as above described, 
to the action of a felt disk, or, still better, of a cloth bob. 

Nickelling of electrotypes, cliches, etc. — The advantages of nickel- 
ling electrotypes, etc., over steeling will be discussed under " Steel- 
ing," and hence only the most suitable composition of the nickel 
baths and the manipulations required will here be discussed. 

The nickel baths according to formula III. (page 148) and for- 
mula VII. (page 150) are the most suitable for simple nickelling, 
because the ammonium sulphate not being present in too great an 
excess, as well as the presence of boric acid, causes the nickel 
to separate with great hardness. With nickelled electro-plates 
three times as large an edition can be printed as with plates 
of the same material not nickelled. 

It being a well-known fact that a fused alloy of nickel with 
cobalt possesses greater hardness than either of the metals by 
themselves, experiments proved that an electro-deposited nickel- 
cobalt alloy exhibited the same behavior, the greatest degree of 
hardness being attained with an addition of cobalt varying be- 
tween 25 and 30 per cent. For this deposit the term hard nickel- 
ling is proposed, the most suitable baths for the purpose being 
prepared according to the following formulae : I. Nickel-ammo- 
nium sulphate 21.16 ounces, cobalt-ammonium sulphate 5.29 
ounces, ammonium sulphate 8.8 ounces, water 15 quarts; or, 
II. Nickel-ammonium sulphate 21.16 ounces, cobalt-ammonium 
sulphate 5.29 ounces, crystallized boric acid 10.58 ounces, 
water 15 quarts. 

Bath No. I. is prepared by simply dissolving the salts in heated 
water, and, in case the bath is too acid, adding spirits of sal 
ammoniac until blue litmus-paper is only slightly reddened. It 
is best to use rolled and cast anodes in equal proportions ; and 
when the bath becomes alkaline to restore its original slightly 
acid reaction by the addition of citric acid. 

To prepare bath No. II. dissolve the constituents by boiling ; 
and in case not entirely neutral metallic salts have been used, add 
to the hot solution, with constant stirring, 1 to If ounces of 



DEPOSITION OF NICKEL AND COBALT. 



183 



nickel carbonate for the neutralization of free sulphuric acid which 
may be present. This bath must not be neutralized, but worked 
with its strongly acid reaction, mixed anodes being also used. 

The bath prepared according to formula No. II. deserves the 
preference, it yielding a harder deposit than bath No. I. 

For the rest, the treatment of the baths is the same as that 
given for nickel baths of similar composition (pp. 148 and 150), 
aud the process of hard nickelling does not essentially differ from 
ordinary nickelling. The suspending hooks are soldered to the 
backs of the plates by means of the soldering-iron and a drop of 
tin ; or the plates are secured in holders of sheet-copper 0.11 inch 
thick, and f to 1 inch wide, of the form shown in Fig. 107. The 
printing surface is freed from grease by brushing with lime-paste, 
rinsed in water, and then brushed with a clean brush to remove 

Fig. 107. 




the lime from the depressions. The plates are then hung in the 
bath and covered with a strong current. When everywhere 
coated with nickel the current is weakened and the deposit 
allowed gradually to augment. With an average duration of 
nickelling of 15 to 20 minutes, with 2.8 to 3 volts, the deposit 
will, as a rule, be sufficiently resisting. 



184 ELECTRO-DEPOSITION OF METALS. 

The nickelled plates are rinsed in water, then plunged in hot 
water, and dried in sawdust, when the nickelled printing surface 
may be brushed over with a brush and fine whiting, it being 
claimed that plates thus treated take printing-ink better, while the 
first impressions of plates not brushed with whiting are somewhat 
dull. 

Nickel-facing is especially suitable for copper plates for color- 
printing, the nickel being not attacked like copper or iron by 
vermilion. 

Recovery of nickel from old baths. — At the present low price 
of nickel its recovery from old solutions scarcely pays. The 
uselessness of the bath is in most cases due to two causes : it 
has either become too poor in metal or it contains foreign me- 
tallic admixtures. In the first case, the expense of evapoi'ating 
with the further manipulation is out of proportion to the value of 
the nickel recovered ; and, in the second case, the reduction of the 
foreign metals is inconvenient and connected with expenses 
making it unprofitable. 

Urquhart proposes the following plan for recovering nickel 
from old solutions : Make a saturated solution of ammonium 
sulphate in warm water, and add to it the old nickel-plating solu- 
tion with constant stirring, and, after the lapse of a few minutes, 
a granular precipitate of the double sulphate of nickel and ammo- 
nium will begin to separate. The addition of ammonium sulphate 
should be continued from time to time until the liquid is colorless. 
The precipitated salt is very pure, and may be used directly in 
making a new bath. 

To improve defective nickelling. — With the basis-metal thoroughly 
cleansed defective places should not occur, but when they happen 
by accident or negligence recourse is had to " doctoring." The 
" doctor" is arranged as follows : A piece of stout copper wire is 
bent in the form of a hook at each end, and a fragment of nickel 
anode is fastened firmly to one of the hooks with a piece of 
twine. The fragment of anode is then wrapped in several folds 
of muslin, the second hook connected by a wire to the anode-rod 
of the bath, and the article put in contact with the negative elec- 
trode. The rag end is now dipped in the nickel bath, applied to 
the defective spot, and allowed to rest upon it for a few moments, 



DEPOSITION OF NICKEL AND COBALT. 185 

then dipped again and reapplied. By repeatedly dipping the rag 
in the nickel bath and applying it in this way a sufficient coating 
of nickel may be given in a few minutes, and if the operation 
is skilfully performed, no trace of the patch will be observable 
after polishing. 

Nickelling by contact and boiling. — Franz Stolba has described 
a nickelling process by contact, which is executed as follows : — 

In a bright copper kettle heat to boiling a concentrated solution 
of zinc chloride with an equal or double the volume of soft water, 
and then add drop by drop pure hydrochloric acid until the pre- 
cipitate formed by diluting the zinc chloride solution with water 
disappears. Then add as much zinc powder as will lie upon the 
point of a knife, the effect of this addition being that the copper 
of the kettle as far as it comes in contact with the solution is in 
a few minutes zincked. Now bring into the kettle sufficient 
nickel salt, best nickel sulphate, to color the fluid perceptibly 
green ; then introduce the articles to be nickelled together with 
small pieces of sheet zinc or zinc wire, so as to present many 
points of contact, and continue boiling. With a correct execution 
of the process it is claimed the articles will be uniformly nickelled 
in 15 minutes; if such is not the case, the boiling must be con- 
tinued, fresh pieces of zinc added, or, if the solution does not 
appear sufficiently green, fresh nickel salt introduced. 

For the success of the process several conditions are necessary. 
The metallic articles must be thoroughly free from grease, as 
otherwise no deposit of nickel is formed on the greasy places. 
In boiling, the solution must not become turbid by the separation 
of basic zinc salt, nor acid by free hydrochloric acid, otherwise 
the nickelling will be dull and blackish. Hence, any turbidity 
must be at once removed by adding drop by drop hydrochloric 
acid, and too great acidity by the careful addition of solution of 
carbonate of soda. The articles thus nickelled are to be thoroughly 
washed with water, dried, and polished with whiting. 

Since stains are readily formed by this process, especially when 
nickelling polished iron and steel articles, on the places where the 
metal to be nickelled comes in contact with the zinc, Stolba in later 
experiments omitted the zinc, and thus the contact process becomes 
a boiling process. To a 10 per cent, solution of zinc chloride add 



186 ELECTRO-DEPOSITION OF METALS. 

enough nickel sulphate to give the solution a deep green color and 
then heat, best in a porcelain vessel, to the boiling-point. Then 
without troubling about the turbidity of the bath caused by the 
separation of a basic zinc salt, immerse the objects, previously 
cleansed and freed from grease, in it in such a way that they do 
not touch each other, or at least in only a few places, and keep 
the whole boiling 30 to 60 minutes, from time to time replacing 
the water lost by evaporation. The after-treatment is the same 
as given above for the contact process ; the deposit of nickel is, of 
course, very thin. 

This process, while suitable for the amateur, cannot be recom- 
mended to the professional electro-plater, the results not being 
sufficiently sure. A thin deposit of nickel of a light color may 
be obtained upon brass articles, but that upon iron articles is dark 
and mostly stained. 

Small articles, which are not to be nickelled by the battery, are 
preferably coated by contact with cobalt by the process to be de- 
scribed later on, under " Electro-cobalting." The higher price 
of cobalt salts makes little difference, small quantities only being 
required, and the color of cobalt can scarcely be distinguished 
from that of nickel. 

By boiling a solution of 8| ozs. of nickel-ammonium sulphate 
and 8 J ozs. of ammonium chloride in 1 quart of water, together 
with clean iron filings free from grease, and introducing into the 
fluid copper or brass articles, the latter become coated with a thin 
layer of nickel capable of bearing light polishing. The nickel 
solution has to be frequently renewed. 

According to R. Kaiser, an alloy containing nickel may be 
deposited upon articles by proceeding as follows : Melt 1 part of 
copper and 5 of tin, and granulate the fused mass by pouring it 
through a heated sheet-iron sieve into a bucket filled with water. 
Boil the granulated metal thus obtained with tartar free from 
lime, and add for every 100 parts by weight of granulated metal 
0.5 part of glowed nickel oxide. Then bring the brass or copper 
articles, previously freed from grease and pickled, into the boiling 
fluid, and after boiling for a short time they will appear coated 
with a white alloy resembling German silver. The addition of 
nickel oxide must be repeated from time to time. Iron and steel 



DEPOSITION OF NICKEL AND CJBALT. 187 

articles are to be previously coppered. By adding nickel car- 
bonate to this bath, it is claimed, coats richer in nickel and of a 
darker color than that of platinum to blue-black are obtained. 

Deposits of nickel alloys. — From suitable solutions of the 
metallic salts nickel may be deposited together with copper and 
tin, as well as with copper and zinc. With the first combination, 
especially, all tones from copper-red to goia shade may be obtained 
according to which metal predominates, or according to the cur- 
rent-strength which is conducted into the bath, as is also the case 
in brassing. 

A suitable bath for coating metallic articles with an alloy of 
nickel, copper, and tin, for which the term nickel-bronze is pro- 
posed, is obtained by dissolving the metallic phosphates in sodium 
pyrophosphate solution. By mixing solution of blue vitriol with 
solution of sodium phosphate, cupric phosphate is precipitated, 
which is filtered off and washed. In the same manner nickel 
phosphate is prepared from a solution of nickel sulphate. These 
phosphates are then, each by itself, dissolved in a concentrated 
solution of sodium pyrophosphate, while chloride of tin is directly 
dissolved in sodium pyrophosphate until the turbidity, at first 
rapidly disappearing, disappears but slowly. 

Nothing definite can be said in regard to the mixing propor- 
tions of these three solutions, because the proportions will have 
to be varied according to the desired color of the deposit ; the 
operator, however, will soon find out of which solution more 
must be added in order to obtain the tone desired. 

For depositing an alloy of nickel, copper, and zinc, solutions 
of cupric sulphate (blue vitriol) and zinc white in potassium 
cyanide, to which is added an ammoniacal solution of nickel car- 
bonate, may be advantageously used. 

According to a French process, a deposit of German silver 
may be obtained as follows : Dissolve a good quality of German 
silver in nitric acid and add, with constant stirring, solution of 
potassium cyanide until all the metal is precipitated as cyanide. 
The precipitate is then filtered off, washed, dissolved in potassium 
cyanide, and the solution diluted with double the volume of 
water. This process, however, does not seem very feasible, since 
nickel separates with difficulty from its cyanide combination. 



188 ELECTEO-DEPOSITION OF METALS. 

Watt recommends the following method : Cut up into small 
pieces sheet German silver about 1 oz., place the strips in a 
glass flask, and add nitric acid diluted with an equal bulk of 
water. Assist the solution of the metal by gentle heat. When 
red fumes cease to appear in the bulb of the flask, decant the 
liquor and apply fresh acid, diluted as before, to the undissolved 
metal, taking care to avoid excess ; it is best to leave a small quan- 
tity of undissolved metal in the flask, by which an excess of acid 
is readily avoided. The several portions of the metallic solutions 
are to be mixed and diluted with about 3 pints of cold water in a 
gallon vessel. Next dissolve about 4 ozs. of carbonate of potash 
in a pint of water, and add this gradually to the former, with 
gentle stirring, until no further precipitation takes place. The 
precipitate must be washed several times with hot water, and 
then redissolved by adding a strong solution of cyanide, with 
stirring, and about 1 oz. of liquid ammonia. To avoid adding 
too great an excess of cyanide, it is a good plan, when the pre- 
cipitate is nearly all dissolved, to let it rest for half an hour or 
so, then decant the clear liquor, and dissolve the remainder of the 
precipitate separately. A small excess of cyanide solution may 
be added as " free cyanide," and the whole mixed together and 
made up to one gallon with cold water. The solution should 
then be filtered or allowed to repose for about 12 hours, and the 
clear liquor then carefully decanted from any sediment which 
may be present from cyanide impurities. The bath must be 
worked with a German-silver anode, which should be of the same 
quality as that from which the solution is prepared; a Bunsen 
battery should be employed as the source of electricity, or a 
dynamo-machine. 

'2. Cobalting. 

Properties of cobalt. — Cobalt has nearly the same color as nickel, 
with a slightly reddish tinge ; its specific gravity is 8.56. It is 
exceedingly hard, highly malleable and ductile, and capable of 
taking a polish. It is slightly magnetic, and preserves this prop- 
erty even when alloyed with mercury. It is rapidly dissolved by 
nitric acid and slowly by dilute sulphuric and hydrochloric acids. 



DEPOSITION OF NICKEL AND COBALT. 189 

For cobalting, the baths given under nickelling may be used 
by substituting for the nickel salt a corresponding quantity of 
cobalt salt. By observing the rules given for nickelling, the 
operation proceeds with ease. Anodes of metallic cobalt are to 
be used in place of nickel anodes. 

Nickel being cheaper and its color somewhat whiter, electro- 
plating with cobalt is but little practised. On account of the 
greater solubility of cobalt in dilute sulphuric acid it is, however, 
under all circumstances, to be preferred for facing valuable copper 
plates for printing. 

According to the more or less careful adjustment of such plates 
in the press, many places of the facing are more or less attacked, 
and it may be desired to remove the coating and make a fresh 
deposit. For this purpose, Gaiffe has proposed the use of cobalt 
in place of nickel, because the former dissolves slowly but com- 
pletely in dilute sulphuric acid. He recommends a solution of 1 
part of chloride of cobalt in 10 of water. The solution is to be 
neutralized with aqua ammonia, and the plates are to be electro- 
plated with the use of a moderate current. 

Cobalt precipitated from its chloride solution does not however 
yield a hard coating, and hence the following bath is recommended 
for the purpose : Double sulphate of cobalt and ammonium 21 
ozs., cobaltous carbonate 0.8 oz., crystallized boric acid 10J ozs., 
water 10 quarts. 

The bath is prepared in the same manner as No. VII., given 
under " Nickelling." It requires a tension of 2.5 to 2.75 volts. 

To determine whether and how much copper is dissolved in 
stripping the cobalt deposit from cobalted copper plates, a copper 
plate with a surface of 7f square inches was coated w T ith 7.71 
grains of cobalt and placed in dilute sulphuric acid (1 part acid 
of 66° Be, to 12.5 parts of water). After the acid had acted for 
16 hours, the cobalt deposit was partially dissolved and had par- 
tially collected in lamina upon the bottom of the vessel, the 
copper plate being entirely freed. On weighing the copper plate 
it was shown that it had lost about 0.0063 per cent., this loss 
being apparently chiefly from the back of the plate, the engraved 
side exhibiting no trace of corrosion. This experiment proved 
that there is no danger of destroying the copper plate by stripping 



190 ELECTRO-DEPOSITION OF METALS. 

the cobalt deposit with dilute sulphuric acid, provided the opera- 
tion is executed with due care and attention. 

Warren has recently described a cobalt solution which can be 
decomposed in a single cell apparatus, and for this reason would 
seem suitable for electro-plating small articles en masse. For the 
preparation of this bath dissolve 3| ounces of chloride of cobalt 
in as little water as possible, and compound the solution with con- 
centrated solution of Rochelle salt until the voluminous precipi- 
tate at first formed is almost entirely redissolved, and then filter. 
Bring the bath into a vessel and place the latter in a clay cell filled 
with concentrated solution of sal ammoniac or of common salt 
and containing a zinc cylinder. Connect the objects to be plated 
to the zinc by a copper wire and allow them to dip in the cobalt 
solution. With a closed current the objects become gradually 
coated with a lustrous cobalt deposit which, after 2 hours, is suffi- 
ciently heavy to bear vigorous polishing with the bob. Zinc may 
be coated in the same manner. 

The following solution has been recommended by Mr. G. W. 
Beardslee, of Brooklyn, N. Y., and is claimed to yield a good 
deposit of cobalt which is very white, exceedingly hard, and ten- 
aciously adherent : Dissolve pure cobalt in boiling hydrochloric 
acid and evaporate the solution to dryness. Next dissolve 4 to 6 
ozs. of the resulting salt in 1 gallon of distilled water, to which 
add liquid ammonia until it turns red litmus-paper blue. The 
solution being thus rendered slightly alkaline is ready for use. 
A battery power of from two to five Smee cells will be sufficient 
to do good work. Care must be had not to allow the solution to 
lose its slightly alkaline condition upon which the whiteness, uni- 
formity of deposit, and its adhesion to the basis-metal greatly de- 
pend. 

For cobalting small fancy articles of copper, brass, or steel, R. 
Daub recommends the following bath : Dissolve 4| ozs. of double 
sulphate of cobalt and ammonium in 4J quarts of water. The 
solution should show, at 59° F., a specific gravity of 1.015. The 
most suitable current-strength is 0.8 ampere with about two volts. 
The size of the anodes is of great influence as regards the uniformity 
of the cobalting. For the deposition of cobalt upon brass, copper, 
steel, or iron, the anodes may consist of rolled cobalt in strips 



DEPOSITION OF NICKEL AND COBALT. 191 

about 2 inches wide and 10 to 12 inches long, according to the 
size of the articles. The anodes are arranged on the sides of the 
vat, about 6 inches apart. With the use of a large vat — holding 
from 500 to 1000 quarts of bath — a corresponding series of such 
anodes are to be suspended to a conducting rod which rests length- 
wise upon the ends of the vat. The metallic articles should be 
coated with a thin film of cobalt in a few seconds after having 
been suspended in the bath, and the current-strength is then re- 
duced, to be increased only when more articles are brought into 
the bath. The mode of treatment is different from that in the 
nickel bath, and, since cobalt deposits with greater ease than 
nickel, the regulation of the current is the principal point. The 
current-strength should be reduced as soon as the articles are 
entirely and nicely coated with cobalt. Copper articles require 
at the beginning a stronger current than brass objects, while for 
articles of iron or steel the current should be weaker than for 
either brass or copper. Places in relief should be kept as far as 
possible from the anodes to prevent blackening or burning. Ac- 
cording to R. Daub, the principal condition for the success of the 
operation is to maintain a uniform density of the bath, either by 
the addition of water or of cobalt salt, as may be required. The 
color of the deposit is much influenced by the current-strength. 
Thus a deposit with 1 volt and a large anode-surface is not so 
white as one with 2 volts and a smaller anode-surface, about ■§ of 
that of the cathode. Cast-brass is especially suitable for cobalt- 
ing, as well as metallic articles which are kept in dry rooms or 
used for ornamental purposes. 

Cobalting by contact. — While nickelling by contact with zinc 
yields only incomplete results, the cobalting of copper and brass 
articles succeeds very well with the use of the following bath : 
Crystallized cobalt sulphate 0.35 oz., crystallized sal ammoniac 
0.07 oz., water 1 quart. Heat the bath to between 104° and 122° 
F., and immerse the previously cleansed and pickled articles in 
the bath, bringing them in contact with a bright zinc surface not 
too small ; for small articles a zinc sieve may be used. In 3 or 
4 minutes the coating is heavy enough to bear vigorous polishing. 



192 ELECTRO-DEPOSITION OP METALS. 



CHAPTER VIII. 

DEPOSITION OF COPPER, BRASS, AND BRONZE. 

1 . Coppering. 

Properties of copper. — Copper has a characteristic red color, and 
possesses strong lustre ; it is very tenacious, may be rolled to thin 
lamina, and readily drawn into fine wire. The specific gravity of 
wrought copper is 8.95, and of cast 8.92. Copper fuses more 
readily than gold, but with greater difficulty than silver. 

In a humid atmosphere containing carbonic acid, copper be- 
comes gradually coated with a green deposit of basic carbonate; 
when slightly heated it acquires a red coating of cuprous oxide, 
and when strongly heated a black coating of cupric oxide with 
some cuprous oxide. Copper is most readily attacked by nitric 
acid, but is slowly dissolved when immersed in heated hydro- 
chloric or sulphuric acid ; with exclusion of the air, it is not dis- 
solved by dilute sulphuric or hydrochloric acid, and but slightly 
with admission of the air. Liquid ammonia causes a rapid 
oxidation of copper in the air and the formation of a blue solu- 
tion. An excess of potassium cyanide dissolves copper. Sul- 
phuretted hydrogen blackens bright copper. 

Copper baths. — The composition of these baths depends on the 
purpose they are to serve, and below are mentioned the most 
approved baths, with the exception of the acid copper bath used 
for plastic deposits of copper, which will be discussed later on 
under " Copper galvanoplasty." 

In most cases the more electro-positive metals, zinc, iron, tin, 
etc., are to be coppered either as preparation for the succeeding 
process of nickelling, silvering, or gilding, or to protect them 
against oxidation, or for the purpose of decoration. The above- 
mentioned electro-positive metals, however, decompose acid copper 
solutions and separate from them pulverulent copper, while an 
equivalent portion of zinc, iron, tin, etc., is dissolved. For this 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 193 

reason, such solutions of copper cannot be used for coating these 
metals for this purpose, alkaline copper baths being exclusively 
employed, which may be arranged under two groups — those con- 
taining potassium cyanide, and those without it. 

Hassauer prepares a copper bath by dissolving 3 J ozs. of copper 
cyanide in a solution of 17 J ozs. of 70 per cent, potassium cyanide 
in 3 quarts of water, boiling, filtering, and diluting with 7 quarts 
of water to a 10 quart bath. This bath works very well when 
heated to between 113° and 122° F., but when used cold requires 
a very strong current, and hence the use of the following formulae 
is recommended : — 

Copper baths for iron and steel articles. — I. To be used at the 
ordinary temperature. — Water 10 quarts, crystallized bisulphite of 
soda 7 ozs., carbonate of soda 14 ozs., neutral acetate of copper 
7 ozs., 75 per cent, potassium cyanide 7 ozs., spirits of sal ammo- 
niac 4.4 ozs. 

II. To be used at between 140° and 158° F. — Water 10 quarts, 
crystallized bisulphite of soda 2f ozs., crystallized carbonate of 
soda 7 ozs., neutral acetate of copper 7 ozs., 75 per cent, cyanide 
of potassium 9f ozs., spirit of sal ammoniac 4 ozs. 

The baths are best prepared as follows : Dissolve the bisulphite 
and carbonate of soda in one-half the water, the potassium cyanide 
in the other half, and mix the copper salt with the spirit of sal 
ammoniac; then pour the blue ammoniacal copper solution into 
the solution of the soda salts, and finally add the potassium 
cyanide solution ; the bath will then be clear and colorless. Boil- 
ing, though not absolutely necessary, is of advantage, after which 
the solution is to be filtered. 

The above formula? are given by Roseleur. However, accord- 
ing to investigations made, the excess of carbonate of soda in 
formula I. serves no special purpose, but on the contrary, in 
many cases, is directly detrimental ; neither is the use of ammonia 
of any special advantage, and it may just as well, or rather better, 
be omitted. Further, the use of separate baths for cold and warm 
coppering is at least questionable. It is believed that a single 
bath suffices for both cases, heating having been found of special 
advantage only for rapid and thick coppering, or for obtaining 
13 



194 ELECTEO-DEBOSITICW OF METALS. 

particular shades which are produced with difficulty iu the cold 
bath, but without trouble in the heated bath. 

The following formula may be highly recommended, a copper 
bath composed according to it always yielding good and sure 

results :— i *V q { v. *'fi \*~ ^ > ^> , r\ y 

III. Water 10 quarts, crystallized ^carbonate of soda &§■ ozs., 
crystallized bisulphite of soda 7 ozs*, neutral acetate of copper 7 
ozs., 98 or 99 per cent, potassium cyanide 8| ozs. -•x^K' ^ 

The bath is prepared as follows : Dissolve in 7 quarts of warm 
water the carbonate of soda, gradually add the bisulphite of soda 
to prevent violent effervescence, and then add, with vigorous 
stirring, tl^ acetate of copper in small portions. Dissolve the 
potassium cyanide in 3 quarts of cold water, and mix both solu- 
tions when the first is cold. By thorough stirring with a clean 
wooden stick, a clear solution is obtained, which is best boiled for 
half an hour and then filtered. This bath does not require a 
strong current, and yields an especially heavy coppering of a 
beautiful red color ; a current of 0.4 ampere at a tension of 3 
to 3.5 volts is calculated for 15 J square inches of surface of 
objects. 9 J 

Annealed sheets of pure copper with as lagge a surface as pos- 
sible serve as anodes. In all baths containing cyanide the anodes 
become, in a comparatively short time, coated with a greenish 
slime consisting of a basic copper cyanide mostly soluble in excess 
of potassium cyanide. When a very thick formation of such slime 
takes place, potassium cyai/de is wanting, and has to be added. 
Other phenomena appearing in copper baths containing cyanide 
may as well here be mentioned. Too large an excess of potassium 
cyanide causes a strong evolution of hydrogen bubbles on the 
objects ; but no deposition of copper, or only a slight one, takes 
place, which besides has the tendency to peel off. If this pheno- 
menon appears after adding potassium cyanide, the excess can be 
readily removed by the addition of copper salt, best cyanide of 
copper, stirred with a small quantity of the bath to a thinly fluid 
paste. After each addition, a test is made whether an objec^ 
suspended in the bath is rapidly aud regularly coppered ; if such 
is not the case, the addition of cyanide of copper is repeated until 
the bath works in a faultless and correct manner. On the other 



DEPOSITION OF COPPEE, BE ASS, AND BEONZE. 195 

hand, a deposit may not. be formed for the want of potassium 
cyanide, which is already indicated by a thick formation of slime 
on the anodes, and by the fluid acquiring a pale blue color ; or 
the metallic content of the bath may be too small. In the first 
case, a slight addition of potassium cyaitide will cause the bath 
to work correctly, but to augment the metallic content of the 
bath, an addition of solution of copper cyanide in potassium 
cyanide is required, it being always best to introduce together 
with the metallic cyanide solution a small quantity of carbonate 
and bisulphite of soda, in order to decrease the resistance to con- 
ductivity. In every bath containing cyanide, each addition, and 
especially that of a metallic salt, causes a momentary irritation, 
and it will be found that a bath augmented by additions works 
irrregularly for some hours. To overcome this, it is recommended 
to boil the bath or work it through with the current as already 
mentioned on p. 139. 

For coppering zinc articles, Roseleur recommends the following 
bath : — 

IV. Water 10 quarts, tartar, free from lime, 6.7 ozs., crystal- 
lized carbonate of soda 15 ozs., blue vitriol 6.7 ozs., caustic soda 
lye of 16° Be. fib. 

To prepare this bath, dissolve the tartar and the crystallized 
carbonate of soda in § of the water, and the blue vitriol in the 
remaining ^, and mix both solutions. Filter off the precipitate, 
dissolve it in the caustic soda lye, and add this solution to the 
other. 

This bath works very well, and may be recommended to 
electro-platers who copper zinc exclusively, but where all kinds 
of metals are to be coppered, bath No. III. is to be preferred, it 
yielding equally good results for zinc. 

For small zinc objects which are to be coppere&in a sieve, bath 
No. III. is used, it being heated for this purpose, and a little 
more potassium cyanide added. Roseleur recommends for the 
same purpose a bath composed as follows : — 

V. Water 10 quarts, crystallized bisulphite of soda If ozs., 
neutral acetate of copper 8 ozs., 75 per cent, potassium cyanide 
12 ^ ozs., and ammonia J oz. The bath is prepared in the same 
manner as formulae I. to III. 



196 ELECTKO-DEPOSITION OF METALS. 

In preparing copper baths, the acetate of copper prescribed in 
the preceding formulas may be replaced by the carbonate or sul- 
phate, the substitution of the latter, after its previous conversion 
into carbonate, being of special advantage in order not to impart 
to the bath too great a resistance by the potassium sulphate, 
formed by reciprocal decomposition. The following formula 
is especially suitable for the use of sulphate of copper (blue 
vitriol) : — 

VI. Blue vitriol . . ... . 10| ozs. 

Crystallized carbouate of soda . . . 10J " 



Water . . . . . . .10 quarts. 

Crystallized bisulphite of soda ... 7 ozs. 

Crystallized carbonate of soda . 

98 to 99 per cent, potassium cyanide 



'2 
'2 



ozs. of blue vitriol and the 10 J ozs. of 
crystallized carbonate of soda, each by itself, in hot water, and 
mix the two solutions ; allow the precipitate of carbonate of cop- 
per to settle, and pour off the supernatant clear fluid. Then pour 
upon the precipitate 5 quarts of water, add the bisulphite of soda, 
next the carbonate of soda, and mix this solution with the solu- 
tion of the potassium cyanide in 5 quarts of water. The fluid 
rapidly becomes clear and colorless, when it is boiled and filtered. 

Of the many directions for copper baths without potassium 
cyanide, to which also belongs the bath prepared according to 
formula IV., and which have chiefly been proposed for coppering 
cast and wrought iron, only a few need be mentioned as being 
actually available. 

Weil obtains a deposit of copper in a bath consisting of a 
solution of blue vitriol in an alkaline solution of tartrate of potas- 
sium or sodium. Such a bath is composed as follows : — 

VII. Water 10 quarts, potassium sodium tartrate (Rochelle 
salt) 53 ozs., blue vitriol 10J ozs., 60 per cent, caustic soda 
28 ozs. 

The chief purpose of the large content of caustic soda is to 
keep the tartrate of copper, which is almost insoluble in water, in 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 197 

solution. According to Weil, the coppering may be executed in 
three different ways, as follows: — 

The iron articles tied to zinc wires or in contact with zinc 
strips are brought into the bath; the coppering thus taking place 
by contact. Or porous clay cells are placed in the bath contain- 
ing the articles ; these clay cells are filled with soda lye in which 
zinc plates connected with the object-rods are allowed to dip, the 
arrangement in this case forming an element with which, by the 
solution of the zinc in the soda lye, a current is produced, which 
effects the decomposition of the copper solution and the deposi- 
tion. When saturated with zinc the soda lye becomes ineffective, 
and, according to Weil, it may be regenerated by the addition of 
sodium sulphide, which separates the dissolved zinc as zinc sul- 
phide. The third method of coppering consists in the use of the 
current of a battery or of a dynamo-machine, in which case cop- 
per anodes have, of course, to be employed. 

A copper bath recommended by Walenn is composed of a solu- 
tion of equal parts of tartrate of ammonia and potassium cyanide, 
in which 3 to 5 per cent, of copper (in the form of blue vitriol or 
moist cupric hydrate) is dissolved. The bath is to be heated to 
about 140° F. 

Copper bath according to Pfanhauser. — Dissolve 2f ozs. of 
cyanide of copper, 1^ drachms each of pure 100 per cent, potas- 
sium cyanide and crystallized sal ammoniac, and 5J drachms of 
ammonia soda in 1 quart of lukewarm water, stirring constantly 
until all the salts are dissolved. 

The temperature of the bath should be between 68° and 77° 
F., and the strength of current 3 volts. Density of current 0.5 
ampere. In case the bath should become poor in metal, cyanide 
of copper has to be added. When the copper anodes become 
coated with too great an abundance of green slime, which does 
not decrease during the night when the bath is not working, 
some potassium cyanide, about \ drachm per quart, should be 
added. 

Gauduin's copper bath consists of a solution of oxalate of 
copper with oxalate of ammonia and free oxalic acid. Fontaine 
asserts that the bath works well, when heated to between 140° 
and 150° F. 



198 ELECTKO-DEPOSITION OF METALS. 

Copper baths containing cyanide cannot be brought into pitched 
vats, vats of stoneware or enamelled iron being used for smaller 
baths, and for larger, basins of brick set in cement, or iron reser- 
voirs lined with ebonite. 

Execution of coppering. — The general rules given under nickel- 
ling, as regards the suitable composition of the bath, correct selec- 
tion of anodes, careful scouring and pickling of the objects and 
proper current-strength also apply to coppering. 

As previously mentioned, annealed sheets of pure copper are 
used as anodes, the surface of which should be at least twice as 
large as that of the objects to be coppered. Even with a correct 
content of potassium cyanide in the bath the anodes readily 
tarnish and must from time to time be brightened by scouring 
with sand or by pickling ; if the latter method be adopted, care 
should be had not to inhale the escaping vapors, which contain 
prussic acid. 

The preliminary scouring and pickling of the articles to be 
coppered are executed according to the directions given on page 
131. The same precautions discussed under nickelling have to 
be used in suspending the objects in the bath, and the directions 
given there for the suitable arrangement of the anodes, etc., also 
apply to coppering ; however, a copper bath conducting better 
than a nickel bath, the distance between the anodes and the 
objects may, if necessary, be somewhat greater. 

With a proper arrangement of the anodes and correct regula- 
tion of the current, the objects should be entirely coated with 
copper in a few minutes after being hung in the bath. In five 
to ten minutes the objects are taken from the bath and brushed 
with a scratch-brush of not too hard brass wires, whereby the 
deposit should everywhere show itself to be durable and adherent. 
Defective places are especially thoroughly scratch-brushed, scoured, 
and pickled; the objects are then returned to the bath. For solid 
and heavy coppering the objects remain in the bath until the 
original lustre and red tone of the coppering disappear and pass 
into a dull discolored brown ; at this stage the objects are again 
scratch-brushed until they show lustre and the red copper color, 
whereby it is of advantage to moisten them with tartar water. 
They are then again returned to the bath, where they remain until 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 199 

the dull discolored tone reappears. They are then taken out, 
scratch-brushed bright, rinsed in several clean waters, plunged 
into hot water, and finally dried, first in sawdust and then 
thoroughly, at a high temperature, in the drying chamber. 
Special attention must be paid to the thorough washing of the 
coppered objects, because, if anything of the bath containing 
cyanide remains in the depressions or pores, small, dark, round 
stains appear on those places which cannot be removed, or at 
least only with great difficulty, they reappearing again in a short 
time after having been apparently removed. This formation of 
stains appears especially frequently upon coppered (as well as 
brassed) iron and zinc castings, which cannot be produced without 
pores. To prevent the formation of these stains the following 
method is recommended : Since the rinsing in many waters, and 
even allowing the objects to lie for hours in running water, offer 
no guarantee that every trace of fluid containing cyanide has been 
removed, the objects are brought into a slightly acid bath which 
decomposes the fluid, a mixture of 1 part of acetic acid and 50 
parts of water being well adapted for the purpose. The objects 
are allowed to remain in this mixture for three to five minutes 
when they are rinsed off in water and dipped for a few minutes 
in dilute milk of lime. They are finally rinsed off and dried. 
Coppered castings thus treated will show no stains. 

O. Shultz obtained a patent for the following method for re- 
moving the hydrochloric acid from the pores, and thus preventing 
the formation of stains : The plated objects are placed in a room 
which can be hermetically closed. The air is then removed from 
the room by the introduction of steam of a high tension, and by 
means of an air-pump, and water sprinkled upon the objects. 
By this treatment in vacuum the fluid in the pores comes to the 
surface and the salt solution is removed by the water sprinkled 
over the articles. 

After drying, the deposit of copper, if it is to show high lustre, 
is polished with soft wheels of fine flannel and dry Vienna lime ; 
commercial polishing red FFF, moistened with a little alcohol, is 
also an excellent polishing agent for copper and all other soft 
metals. 

As is well known, massive copper rapidly oxidizes in a humid 



200 ELECTRO-DEPOSITION OF METALS. 

atmosphere, and this is the case to a still greater extent with 
electro-deposited copper. Hence, the coppered objects, if they 
are not to be further coated with a non-oxidizing metal, have to 
be provided with a colorless, transparent coat of lacquer (see 
"Lacquering"). 

It frequently happens that slightly coppered (as well as slightly 
brassed) objects, especially of zinc, after some time, become entirely 
white and show no trace of the deposit. This is due to the deposit 
penetrating into the basis-metal, as already explained on p. 140. 
Lacquering in this case is of no avail, the deposit also disappear- 
ing under the coat of lacquer. The only remedy against this 
phenomenon is a heavier deposit. 

If the coppered objects are to be coated with another metal, 
drying is omitted, and after careful rinsing they are directly 
brought into the respective bath, or into the quicking pickle, if, 
as, for instance, in silvering, quicking has to be done. In such 
cases, where the copper deposit serves only as an intermediary for 
the reception of another metallic coating, the objects need not to 
be coppered as thickly, as previously described, by treating them 
three times in the bath. Preliminary coppering for 5 to 10 
minutes suffices in all cases, which is succeeded by scratch -brush- 
ing in order to be convinced that the deposit adheres firmly and 
that the basis-metal is uniformly coated. The objects are then 
hung in the bath for 5 to 10 minutes longer with a weak current. 
In coppering sheet iron or sheet zinc which is to be nickelled, the 
sheets are taken from the bath after 3 to 5 minutes, at any rate 
while they still retain their lustre, scratch-brushing being in this 
case omitted. For coppering such sheets a current-density of 0.5 
ampere with a tension of 3.5 to 4 volts is required. The treat- 
ment of copper baths, when they become inactive or exhibit other 
abnormal phenomena, has been referred to on p. 194; all other 
rules for galvanic baths given in Chap. VI. must here also be 
observed. 

For coppering small articles en masse in sieves it is recom- 
mended to have the copper baths right hot ; for the rest, the pro- 
cess is the same as that given for nickelling small articles en masse 
on p. 162, 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 201 

Coppering by contact and dipping. — According to Liidersdorff, 
a solution of tartrate of copper in neutral potassium tartrate serves 
for this purpose. A suitable modification of this bath is as fol- 
lows : Heat 10 quarts of water to 140° F., add 2 lbs. of pulver- 
ized tartar (cream of tartar) free from lime, and 10J ozs. of car- 
bonate of copper. Keep the fluid at the temperature above 
mentioned until the evolution of gas due to the decomposition of 
the carbonate of copper ceases, aud then add in small portions, 
and with constant stirring, pure whiting until effervescence is no 
longer perceptible. Filter off the fluid from the tartrate of lime 
separated and wash the precipitate so that the filtrate, inclusive of 
the wash water, amounts to JO or 12 quarts. 

Zinc is coppered in this bath by simple immersion ; other 
metals have to be brought in contact with zinc. 

To coat zinc plates with a very thin but hard layer of copper, 
immerse the plates in a bath composed of 100 parts of water sat- 
urated with cupric chloride — cupric chloride 40 parts, water 60 — 
150 parts of ammonia and 3000 parts of water. For very solid 
coppering, the above-described bath, which is of a beautiful blue 
color, is used, and a saturated solution of potassium cyanide in 
water added until the blue of the first mixture has quite disap- 
peared. For plates engraved with the burin or for stamped 
plates, it is best to use a mixture of cyanide of copper with neutral 
potassium sulphate, to which is added a mixture of a saturated 
solution of blue vitriol in water and of water saturated with 
cyanide of copper. The bath is ready for use when the precipi- 
tate is completely dissolved and the fluid entirely discolored. 

Another contact coppering bath is that prepared according to 
formula "VII. (p. 196), proposed by Weil. In this bath zinc is 
also coppered by simple immersion, and copper and iron in con- 
tact with zinc strips. 

According to Bacco, a copper bath in which zinc may be cop- 
pered by immersion, and iron and other metals in contact with 
zinc, is prepared by adding to a saturated solution of blue vitriol, 
potassium cyanide solution until the precipitate of cyanide of 
copper which is formed is again dissolved. Then add -^ to j* of 
the volume of liquid ammonia and dilute with water to 8° Be. 

The so-called brush-coppering which has been recently recom- 



202 ELECTRO-DEPOSITION OF METALS. 

mended ma} r here be mentioned. This process may be of practi- 
cal advantage for coppering very large objects which by another 
method could only be coated with difficulty. The deposit of 
copper is, of course, very thin. The process is executed as fol- 
lows : The utensils required are two vessels of sufficient size, each 
provided with a brush, preferably so wide that the entire surface 
of the object to be treated can be coated with one application. 
One of the vessels contains a strongly saturated solution of caustic 
soda, and the other a strongly saturated solution of blue vitriol. 
For coppering, the well-cleansed object is first uniformly coated 
with a brushful of the caustic soda solution, and then also with a 
brushful of the blue vitriol solution. A quite thick film of copper 
is immediately deposited upon the object. Care must be had not 
to take the brush too full and not to touch the places once gone 
over, the second time, as otherwise the layer of copper does not 
adhere firmly. 

Many iron and steel objects are provided with a thin film of 
copper in order to give them a more pleasing appearance. For 
this purpose a copper solution of 10 quarts of water, If ozs. of 
blue vitriol, and If ozs. of pure concentrated sulphuric acid may 
be used. Dip the iron or steel objects, previously freed from 
grease and oxide, for a moment in the solution, moving them con- 
stantly to and fro ; then rinse them immediately in ample water, 
and dry. By keeping the articles too long in the solution the 
copper separates in a pulverulent form and does not adhere. 

Steel pens, needles, eyes, etc., may be coppered by diluting the 
copper solution just mentioned with double the quantity of water, 
moistening sawdust with the solution and revolving the latter, 
together with the articles to be coppered, in a wooden tumbling 
box (p. 109). 

The inlaying of depressions of coppered art-castings with black 
may be done in different ways. Some blacken the ground by ap- 
plying a mixture of spirit lacquer with lampblack and graphite, 
while others use oil of turpentine with lampblack and a few drops 
of copal lacquer. A very thin nigrosin lacquer mixed with finely 
pulverized graphite is very suitable for the purpose. When the 
lacquer is dry the elevated places which are to show the copper 
color are cleansed with a linen rag moistened with alcohol. 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 203 

Electrolytically coppered articles may be inlaid black by coat- 
ing them, after thorough scouring and pickling, with arsenic in 
one of the baths given under " Electro-deposition of Arsenic," 
and, after drying in hot water and sawdust, freeing the surfaces 
and profiles, which are to appear coppered, from the coating of 
arsenic by polishing upon a felt wheel. If this polishing is to be 
avoided, the portions which are not to be black may be coated 
with covering lacquer, and arsenic deposited upon the places 
remaining free. 

For coloring, platinizing, and oxidizing of copper, see the proper 
chapter. 

2. Brassing (Cuivre-poli Deposit). 

Brass is an alloy of copper and zinc whose color depends on 
the quantitative proportions of both metals. The alloys known 
as yellow brass, red brass (similor, tombac), consist essentially of 
copper and zinc, while those known as bell metal, gun metal, and 
the bronzes of the ancients are composed of copper and tin. 
Modern bronzes contain copper, zinc, and tin. 

The behavior of brass towards acids is nearly the same as that 
of copper ; it oxidizes, however, less readily in the air, is harder 
than copper, malleable, and can be rolled and drawn into wire. 

Brass baths. — According to the plan pursued in this work, only 
the most approved formulae will be given. There exists a large 
number of directions for brass baths ; but we share the opinion of 
Roseleur, that a brass bath containing copper and zinc salts in 
nearly equal proportions is the most suitable and least subject to 
disturbances. A brass bath is to be considered as a mixture of 
solutions of cyanide of copper and cyanide of zinc, or of other 
copper-zinc salts in the most suitable solvent ; and since a solu- 
tion of cyanide of copper requires a different current-strength 
from one of zinc salt, it will be seen that according to the greater 
or smaller current-strength, now more of the one, and now more 
of the other metal is deposited, which, of course, influences the 
color of the deposit. Hence the proper regulation of the current 
is the chief condition for obtaining beautiful deposits, let the 
bath be composed as it may. 



204 ELECTRO-DEPOSITION OF METALS. 

For all baths containing more than one metal in solution, it 
may be laid down as a rule that the less positive metal is first 
deposited. In a brass bath copper is the negative and zinc the 
positive metal ; and hence a weaker current deposits more copper, 
in consequence of which the deposit becomes redder, while, viee 
versa, a more powerful current decomposes besides the copper 
solution also a larger quantity of zinc solution and reduces zinc, 
the color produced being more pale yellow to greenish. By bear- 
ing this in mind it is not difficult to obtain any desired shades 
within certain limits. 

I. Brass bath according to Roseleur. — Blue vitriol and zinc 
sulphate (white vitriol), of each 5£ ounces, and crystallized car- 
bonate of soda 15§ ounces. Crystallized carbonate of soda and 
crystallized bisulphite of soda, of each 7 ounces, 98 per cent, 
potassium cyanide 8f ounces, arsenious acid 30f grains, water 10 
quarts. 

The bath is prepared as follows : In 5 quarts of warm water 
dissolve the blue vitriol and the zinc sulphate ; and in the other 
5 quarts the 1 5f ounces of carbonate of soda ; then mix both 
solutions, with stirring. A precipitate of carbonate of copper 
and carbonate of zinc is formed, which is allowed quietly to settle 
for 10 to 12 hours, when the supernatant clear fluid is carefully 
poured off, so that nothing of the precipitate is lost. Washing 
the precipitate is not necessary ; the clear fluid poured off is of no 
value and is thrown away, Now add to the precipitate so much 
water that the resulting fluid amounts to about 6 quarts, and dis- 
solve in it, with constant stirring, the carbonate and bisulphite 
of soda, adding these salts, however, not at once, but gradually, in 
small portions, to avoid foaming over by the escaping carbonic acid. 
Dissolve the potassium cyanide in 4 quarts of cold water and add 
this solution, with the exception of about J pint, in which the 
arsenious acid is dissolved with the assistance of heat, to the first 
solution, and finally add the solution of arsenious acid in the J 
pint of water retained, when the bath should be clear and color- 
less. If after continued stirring particles of the precipitate remain 
undissolved, carefully add somewhat more potassium cyanide 
until solution is complete. 

Fresh brass baths work, as a rule, more irregularly than any 



DEPOSITION OF COPPEE, BEASS, AND BEONZE. 205 

other baths containing cyanide, the deposit being either too red 
or too green or gray, while frequently one side of the object is 
coated quite well, and the other not at all. To force the bath to 
work correctly it must be thoroughly boiled, the water which is 
lost by evaporation being replaced by the addition of distilled 
water or pure rain water. If boiling is to be avoided, the bath, 
as previously mentioned, is worked through for hours, and even 
for days, with the current, until an object suspended in it is cor- 
rectly brassed. 

The addition of a small quantity of arsenious acid is claimed to 
make the brassing brighter ; but the above mentioned proportion 
of 30f- grains for a 10 quart bath must not be exceeded, as 
otherwise the color of the deposit would be too light and show a 
gray tone. 

II. Crystallized carbonate of soda 10J ounces, crystallized 
bisulphite of soda 7 ounces, neutral acetate of copper 4.4 ounces, 
crystalized chloride of zinc 4.4 ounces, 98 per cent, potassium 
cyanide 14.11 ounces, arsenious acid 30f grains, water 10 quarts. 

The preparation of this bath is more simple than that of the 
preceding. 

Dissolve the carbonate and bisulphite of soda in 4 quarts of 
water, then mix the acetate of copper and chloride of zinc with 
2 quarts of water, and gradually add this mixture to the solution 
of the soda salts. Next dissolve the potassium cyanide in 4 quarts 
of water, and add this solution to the first, retaining, however, a 
small portion of it, in which dissolve the arsenious acid with the 
assistance of heat. Finally add the arsenious acid solution, when 
the bath will become clear. Boiling the bath, or working it 
through with the current, is also required. 

For brassing iron in this bath the addition of carbonate of soda 
may be increased up to 35 ounces for a 10 quart bath, this being 
also permissible, when frequent scratch-brushing is to be avoided 
in coating zinc articles with a heavy deposit of brass ; because it 
seems that a large content of carbonate of soda in the bath con- 
siderably retards the changing of the brass color into a discolored 
brown, though the brilliancy of the deposit appears to suffer some- 
what. When boiled from 1 to 2 hours, or worked through with 
the current for 10 to 12 hours, the bath prepared according to 



206 ELECTRO-DEPOSITION OF METALS. 

formula II. works very well ; it requires a current of 0.5 to 0.55 
ampere, with a tension of 3.5 to 4 volts per 15J square inches 
surface. 

As previously mentioned, the color of the deposit depends on 
the proportional quantity in which copper and zinc are present, 
a strong current depositing more zinc and a weak current more 
copper. By diminishing or increasing the current-strength by 
means of the resistance board, a deposit of a redder or more pale 
yellow to greenish color can be produced. However, with a bath 
which does not contain copper and zinc in the correct proportional 
quantities, and especially with old baths long in use, a determined 
color of the deposit cannot be produced with the assistance of the 
resistance board. In such case the content of the metal lacking 
in the bath, which is required for the production of a determined 
color, must be augmented by the addition of solution of the re- 
spective metallic salt in potassium cyanide. 

Suppose a bath which originally contained copper and zinc 
salts in equal proportions has been long in daily use. Now, 
since brass contains more copper than zinc, it is evident that 
more of the former will be withdrawn from the bath than of the 
latter, and finally a limit will be reached when the bath with a 
current suitable for the decomposition of the solution will deposit 
a greenish or gray brass, and with a weaker current produce no 
deposit whatever. The only help in such a case is the addition 
of sufficient solution of cyanide of copper in potassium cyanide, 
so that, even with quite a powerful current, a deposit of a beauti- 
ful brass color is produced, the shades of which can then again 
be controlled with the help of the resistance board. However, it 
must not be forgotten that every addition of a metallic salt 
momentarily irritates the brass bath, making it, so to say, sick, 
and to confine this phenomenon to the narrowest limit, an addition 
of carbonate and bisulphite of soda should at the same time be 
made, and the bath be worked through with the current as pre- 
viously described, until a test shows that it works in a regular 
manner. 

Annealed sheets of brass not rolled too hard, and of as nearly 
as possible the same composition and color the deposit is to show, 
are used as anodes. The anode-surface should be at least twice 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 207 

as large as that of the objects to be brassed, though it is best to 
use as many anodes as the anode-rods will hold. 

As in the copper bath, an abundant formation of slime on the 
auodes indicates the want of potassium cyanide in the bath. In 
this case the evolution of gas bubbles on the objects is very 
slight, aud the deposit forms slowly. This is remedied by an ad- 
dition of potassium cyanide. The slow formation of the deposit, 
however, may also be due to a want of metallic salts ; in this case 
not only potassium cyanide, but also solution of cyanide of copper 
and cyanide of zinc in potassium cyanide, has to be added. For 
this purpose prepare a concentrated solution of potassium cyanide 
in water, and a solution of equal parts of blue vitriol and zinc 
sulphate in water. From the latter precipitate the copper and 
zinc as carbonates with a solution of carbonate of soda as given in 
formula I., p. 204. After allowing the precipitate to settle pour 
off the clear supernatant fluid and add to the precipitate, with 
vigorous stirring, of the potassium cyanide solution, until it is 
dissolved ; if heating takes place thereby, add from time to time 
a little cold water. Add this solution with a small excess of 
potassium cyanide, and the addition of carbonate or bisulphite of 
soda, to the bath, and boil the latter or work it through with the 
current. A more simple method is to procure cyanide of copper 
and cyanide of zinc, or concentrated solutions of these combinations, 
from a dealer in such articles. In the first case rub in a mortar 
equal parts of cyanide of zinc and cyanide of copper with water 
to a thickly fluid paste. Pour this paste into potassium cyanide 
solution, containing about 7 ozs. of potassium cyanide to the 
quart, as long as the metallic cyanides dissolve quite rapidly with 
stirring. When solution takes place but slowly, stop the addition 
of paste. 

When a brass bath contains too large an excess of potassium 
cyanide, a very vigorous evolution of gas takes place on the 
objects, but the deposit is formed slowly or not at all ; besides 
the deposit formed has a tendency to peel off in scratch-brushing. 
In this case the injurious excess has to be removed, which is 
effected by pouring, with vigorous stirring, a quantity of the 
cyanide above-mentioned thinly fluid paste of cyanide of zinc and 
of copper into the bath. 



208 ELECTRO-DEPOSITION OF METALS. 

III. Crystallized carbonate of soda 10J ozs., crystallized bisul- 
phite of soda 7 ozs., cyanide of copper and cyanide of zinc of 
each 3J ozs., water 10 quarts, and enough 98 per cent, potassium 
cyanide to render the solution clear. 

To prepare the bath dissolve the carbonate and bisulphite of 
soda in 2 to 3 quarts of water, rub in a porcelain mortar the 
cyanide of copper and cyanide of zinc with a quart of water to 
a thin paste, add this paste to the solution of the soda salts and 
finally add, with vigorous stirring, concentrated potassium cyan- 
ide solution until the metallic cyanides are dissolved. Dilute the 
volume to 10 quarts, and, for the rest, proceed as given for 
formulae I. and II. 

For brassing zinc exclusively, Roseleur recommends the fol- 
lowing bath : — 

IV. Dissolve 9f ozs. of crystallized bisulphite of soda and 14 
ozs. of 70 per cent, potassium cyanide in 8 quarts of water, and 
add to this solution one of 4f ozs. each of neutral acetate of cop- 
per and crystallized chloride of zinc, 5J ozs. of aqua ammonia, 
and 2 quarts of water. 

For brassing cast-iron, wrought-iron, and steel, Gore highly 
recommends the following composition : — 

V. Dissolve 35£ ozs. of crystallized carbonate of soda, 7 ozs. 
of crystallized bisulphite of soda, 13^ ozs. of 98 per cent, potas- 
sium cyanide in 8 quarts of water; then add, with constant 
stirring, a solution of fused chloride of tin 3J ozs., and neutral 
acetate of copper 4£ ozs., in 2 quarts of water. Boil and filter. 
This bath works best with a current of 3.75 volts. 

According to Norris and Johnson, a good brass bath is said to 
be obtained as follows : — 

VI. Carbonate of ammonia 35^ ozs., 70 per cent, potassium 
cyanide 35J ozs., cyanide of copper and cyanide of zinc, each 2| 
ozs., water 10 quarts. 

The large content of potassium cyanide in this bath is unin- 
telligible. 

A solution for transferring any copper-zinc alloy serving as 
anode is composed, according to Hess, as follows : — 

VII. Bisulphite of soda 14| ozs., crystallized sal ammoniac 9| 
ozs., 98 per cent, potassium cyanide 2| ozs., water 10 quarts. 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 209 

Cast metal plates are to be used as anodes. The transfer begins 
after a medium strong current has, for a few hours, passed through 
the bath. This bath is also well adapted for the deposition of 
tombac, with the use of tombac anodes ; and the most suitable 
tension of the current is 3 to 3.5 volts. 

VIII. For brassing all kinds of metals Wm. Pfanhauser, of 
Vienna, recommends the following bath : — 

Dissolve If ozs. each of cyanide of copper and cyanide of zinc, 
1| drachms of pure 100 per cent, potassium cyanide, 1^ drachms 
of crystallized sal ammoniac, and 5f drachms of ammonia-soda 
in 1 quart of lukewarm water, stirring constantly until all the 
salts are dissolved. The bath is ready for immediate use, and 
does not require boiling or previous working through with the 
current. 

The temperature of the bath should be between 68° and 77° F. 
For brassing zinc the current should have a strength of 2J volts, 
for iron 3 volts, for chains 3 to 3| volts, and for small articles 
en masse 4 volts. Density of the current, 0.5 ampere. 

From the composition of this bath it will be seen that it con- 
tains quite a large content of metal, If ozs. of cyanide of copper 
being equal to about 6f drachms of copper, and If ozs. of cyanide 
of zinc to about 5f drachms of zinc. Hence the bath contains 
about 12^ drachms of brass per quart. 

Brassing in this bath succeeds equally well with all kinds of 
metals, the result being a uniform deposit of metal while the 
color, even of thick deposits, is a fiery sad yellow. Small articles, 
which are suspended en masse in dipping baskets, as well as steel 
chains, and even cast-iron, which is notoriously difficult to brass, 
become rapidly coated in this bath. In case the brass anodes 
become coated with too great an abundance of green slime, 
which decreases during the night when the bath is not work- 
ing, some potassium cyanide, about If drachms per quart, should 
be added. Of course, the bath must be supplied from time to time 
with additions of fresh cyanide of copper and cyanide of zinc. 

Execution of brassing. — To avoid unnecessary repetition, we 
refer, as regards the practice of brassing, to what has been said 
under " Execution of Coppering," the manipulations being the 
14 



210 ELECTRO-DEPOSITION OF METALS. 

same, while the treatment of the brass baths has already been 
sufficiently discussed in the preceding pages. 

The deposition of several metals from a common solution is 
not an easy task, and requires attention and experience ; if, how- 
ever, the directions given in this chapter are followed, the operator 
will be able to conduct, after short experience, the brassing pro- 
cess with the same success as one in which but one metal is 
deposited. 

In brassing, the distance of the objects to be brassed from the 
anodes is of considerable importance. If objects with deep de- 
pressions or high reliefs are hung in the brass bath, it will be 
found that, with the customary distance of 3f to 5| inehes from the 
anodes, the brassing of the portions in relief nearest to the anodes 
will turn out of a lighter color than that of the depressed portions, 
which will show a redder deposit, the reason for this being that 
the current acts more strongly upon the portions in relief, and 
consequently deposits more zinc than the weaker current, which 
strikes the depressions. To equalize the difference, the objects 
have to be correspondingly further removed from the anodes, with 
lamp-feet up to 9f inches, and even more, when a deposit of the 
same color will be everywhere formed. 

The brassing of unground iron castings is especially trouble- 
some, and in order to obtain a beautiful and clean deposit the 
preliminary scratch-brushing has to be executed with special 
care ; but even then the color of the brass deposit will sometimes 
be found to possess a disagreeable gray tone. This is very likely 
largely due to the quality of the iron itself, and it is advisable 
first to give the casting a thin coat of nickel or tin, upon which a 
deposit of brass of the usual brilliancy can be produced. In 
baths serving for brassing iron articles, a large excess of potas- 
sium cyanide must be avoided ; it is, however, an advantage to 
increase the content of carbonate of soda. 

Brassing by contact and dipping. — Some authors have given 
directions for brassing by contact — for instance, Bacco, Weil, and 
others — but the results obtained are so unsatisfactory, and the 
process so uncertain, that it is not necessary to enter into further 
details. 



DEPOSITION OF COPPER, BRASS, AND BRONZE. 211 

The inlaying with black of brassed articles is done in the same 
manner as described under " Coppering." 

For oxidizing, platinizing, and coloring of brass, see the proper 
chapter. 

3. Bronzing. 

The electrolytic coating of metallic objects with bronze, i. e., a 
copper-tin alloy, or an alloy of copper, tin, and zinc, is but seldom 
practised, the bronze tone being in most cases imitated by a 
deposit of brass, with a somewhat larger content of copper. 

For coating wrought- and cast-iron with bronze, Gountier re- 
commends the following solution : — 

Yellow prussiate of potash 10J ozs., cuprous chloride 5J ozs., 
stannous chloride (tin salt) 14 ozs., sodium hyposulphite 14 ozs., 
water 10 quarts. 

According to Puolz, a bronze bath is prepared as follows : 
Dissolve at 122° to 140° F., cyanide of copper 2.11 ozs., and 
oxide of tin 0.7 oz. in 10 quarts of potassium cyanide solution of 
4° Be. The solution is to be filtered. 

Eisner prepares a bronze bath by dissolving 21 ozs. of blue 
vitriol in 10 quarts of water, and adding a solution of 2| ozs. of 
chloride of tin in potash lye. 

Salzede recommends the following bath, which is to be used at 
between 86° and 95° F. : Potassium cyanide 3| ozs., carbonate 
of potash 35£ ozs., stannous chloride (tin salt) 0.42 oz., cuprous 
chloride | oz., water 10 quarts. 

Weil and Newton claim to obtain beautiful bronze deposits 
from solutions of the double tartrate of copper and potash, and 
the double tartrate of the protoxide of tin and potash, with 
caustic potash, but fail to state the proportions. 

The above formulse are here given with all reserve, since ex- 
periments with them failed to give satisfactory results; with 
Gountier's, Ruolz's, and Eisner's baths no deposit was obtained, 
but only a strong evolution of hydrogen, while even with a 
strong current Salzede's bath did not yield a bronze deposit, but 
simply one of tin. 

The following method of preparing a bronze bath may be recom- 
mended : Prepare, each by itself, solutions of phosphate of copper 



212 ELECTRO-DEPOSITION OF METALS. 

and stannous chloride (tin salt) in sodium pyrophosphate. From 
a blue vitriol solution precipitate, with sodium phosphate, phos- 
phate of copper, allow the latter to settle, and after pouring off the 
clear supernatant fluid bring it to solution by concentrated solu- 
tion of sodium pyrophosphate. On the other hand, add to a satu- 
rated solution of sodium pyrophosphate solution of tin salt as long 
as the milky precipitate formed dissolves. Of these two metallic 
solutions add to a solution of sodium pyrophosphate, which con- 
tains about If ozs. of the salt to the quart, until the precipitate 
appears quickly and of the desired color. For anodes, use cast 
bronze plates, which dissolve well in the bath. Some sodium 
phosphate has from time to time to be added to the bath, and if 
the color becomes too light, solution of copper, and if too dark, 
solution of tin. 

For deposits of tombac Hess's bath (formula VII., brassing) 
with anodes of plate or sheet tombac can be recommended ; 3 to 
3.5 volts being the most suitable tension of the current for the 
decomposition of the bath. 

For nickel bronze, see p. 186. 

The execution of bronzing requires the same attention and 
manipulations as those given for brassing. 



CHAPTER IX. 

DEPOSITION OF SILVER. 

Properties of silver. — Pure silver is the whitest of all known 
metals ; it takes a fine polish, is softer and less tenacious than 
copper, but harder and more tenacious than gold. It is very 
malleable and ductile, and can be obtained in exceedingly thin 
leaves and fine wire. Its specific gravity is 10.48 to 10.5, accord- 
ing to whether it is cast or hammered. It melts at about 1832° F. 
It is unacted upon by the air, but in the atmosphere of towns it 
gradually becomes coated with a film of silver sulphide. It is 
rapidly dissolved by nitric acid, nitrogen dioxide being evolved ; 
hydrochloric acid has but little action upon it even at boiling 



DEPOSITION OF SILVER. 213 

heat ; when heated with concentrated sulphuric acid it yields sul- 
phur dioxide and silver sulphate. 

Silver baths. — Only formula? for approved baths will be given. 

Silver bath for a heavy electro-deposit of silver (silvering by 
weight). — I. 98 per cent, potassium cyanide 14 ozs., fine silver 
as silver chloride 8f ozs., distilled water 10 quarts. 

la. 98 per cent, potassium cyanide 8f ozs., fine silver as silver 
cyanide 8f ozs., distilled water 10 quarts. 

Before describing the preparation of the bath a few words may 
be said in regard to the old dispute whether it is preferable to use 
silver cyanide or silver chloride. Without touching upon all the 
arguments advanced, it may be asserted by reason of conscientious 
comparative experiments that the results are the same and that 
the life of the bath is also the same whether one or the other salt 
has been used in the original preparation. From a theoretical 
standpoint, silver cyanide must be given the preference ; but as 
the disadvantages in respect to the life of the bath ascribed by 
some to silver chloride do not exist, it might be advisable for 
those who prepare their own baths to use silver chloride. 

Preparation of bath I. with silver chloride. — Dissolve 14 ozs. of 
chemically pure nitrate of silver, best the crystallized and not the 
fused article, in 5 quarts of water, and add to the solution pure 
hydrochloric acid or common salt solution, with vigorous stirring 
or shaking, until a sample of the fluid filtered through a paper 
filter forms no longer a white caseous precipitate of silver chloride 
when compounded with a drop of hydrochloric acid. These, as 
well as the succeeding operations until the silver chloride is com- 
plete, have to be performed in a darkened room, as silver chloride 
is partially decomposed by light. Now separate the precipitate 
of silver chloride from the solution by filtering, using best a large 
bag of close felt, and wash the precipitate in the felt bag with 
fresh water. Continue the washing until blue litmus-paper is no 
longer reddened by the wash-water, if hydrochloric acid was used 
for precipitating, or, if common salt solution was used, until a small 
quantity of the wash-water on being mixed with a drop of lunar 
caustic solution produces only a slight milky turbidity and no pre- 
cipitate. Now bring the washed silver chloride in portions from 
the felt bag into a porcelain mortar,. rub it with water to a thin 



214 ELECTKO-DEPOSITION OF METALS. 

paste and pour the latter into the potassium cyanide solution con- 
sisting of 14 ozs. of 98 per cent, potassium cyanide in 5 quarts 
of water, in which, with vigorous stirring, the silver chloride 
gradually dissolves. All the precipitated silver chloride having 
been brought into solution, dilute with water to 10 quarts of fluid 
and boil the bath, if possible, for one hour, replacing the water 
lost by evaporation. A small quantity of black sediment con- 
taining silver thereby separates from which the colorless fluid is 
filtered off". The sediment is added to the silver residues and is 
worked together with them for the recovery of the silver by one 
of the methods to be described later on. 

Preparation of bath la. with silver cyanide.— Dissolve 14 ounces 
of chemically pure crystallized nitrate of silver in 5 quarts of 
water, and precipitate the silver with prussic acid, adding the 
latter until no more precipitate is produced by the addition of a 
few drops of prussic acid to a filtered sample of the fluid. Now 
filter, wash out, and proceed for the rest exactly as stated for the 
bath with silver chloride, except that only 8f ounces of potassium 
cyanide are taken for dissolving the silver cyanide. In working 
with prussic acid avoid inhaling the vapor which escapes from 
the liquid prussic acid, especially in the warm season of the year ; 
and be careful the acid does not come in contact with cuts on the 
hands. It is one of the most rapidly acting poisons. 

Cyanide of silver may also be prepared as follows : Dissolve 
14 ounces of chemically pure crystallized nitrate of silver in 5 
quarts of water, and add moderately concentrated potassium 
cyanide solution until no more precipitate is formed, avoiding, 
however, an excess of the precipitating agent, as it would again 
dissolve a portion of the cyanide of silver. The precipitated 
cyanide of silver is filtered off, washed and dissolved in potassium 
cyanide, as above described. 

The bath prepared according to formula I. or la., serves chiefly 
for thickly silvering objects of German silver ; it may, however, 
be used for silvering other metals by weight. 

Silver bath for ordinary electro-silvering. — II. 98 per cent, 
potassium cyanide 6J to 7 ounces, fine silver (as silver nitrate or 
chloride), 3 J ounces; distilled water, 10 quarts. 

To prepare the bath dissolve 5J ounces of chemically pure 



DEPOSITION OF SILVER. 215 

crystallized nitrate of silver in 5 quarts of distilled water; in the 
other 5 quarts of water dissolve the potassium cyanide, and mix 
both solutions. Or, if chloride of silver is to be used, precipitate 
the solution of 3J ounces of the silver salt in the same manner as 
given for formula I.; wash the precipitated chloride of silver, 
and dissolve it in the potassium cyanide solution. 

Vats of stoneware, enamelled iron, or lined with ebonite mass 
are to be used for the silver baths. 

Treatment of the silver baths; silver anodes. — Frequently the 
error is committed of adding too much potassium cyanide to the 
baths. A certain excess of it must be present, and is taken into 
consideration in the formulae given. For dissolving the cyanide 
of silver prepared from 14 ounces of nitrate of silver, as given 
in formula la., only about 5J ounces of potassium cyanide are 
required, and the consequence of working with such a bath devoid 
of all excess would be that, on the one hand, the bath would oifer 
a considerable resistance to the current, and, on the other, that the 
deposit of silver would not be uniform and homogeneous. Hence 
with the use of a medium strong current about 30 to 35 per cent, 
more of potassium cyanide than fine silver is taken. In working 
with a stronger current, this excess would, however, be too large, 
in consequence of which the deposit would not adhere properly 
and would peel off in scratch-brushing. And again, with a weak 
current the baths can, without disadvantage, stand a larger excess. 
As a rule, however, the proportion between fine silver and potas- 
sium cyanide in the above formula may be considered as normal, 
and the current-strength will have to be regulated so that a de- 
posit of fine structure, which adheres firmly, is formed. The most 
suitable current-strength per 15 J square inches of surface is 0.25 
to 0.15 ampere, and 0.5 to 0.75 volt tension; the tension of a 
Daniell element being more than sufficient for the decomposition 
of the silver bath. On account of the silver bath requiring a 
current of slight electro-motive force, the Smee element, which 
yields 0.48 volt, is much liked for silvering in this country and 
in England. The Bunsen element may, however, also be used if 
the surface to be silvered is made to correspond with the energy 
of such an element ; or if a resistance board is placed in the 
circuit, which is advisable in all cases. On account of the slight 



216 ELECTEO-DEPOSITION OF METALS. 

electro-motive force required in silvering larger surfaces of objects, 
the elements are not to be coupled one after the other for electro- 
motive force, but alongside one another for quantity. In no case 
must an evolution of hydrogen be perceptible on the articles, and 
the current must be more weakened the larger the excess of potas- 
sium cyanide in the bath. 

Whether too much, or not enough, potassium cyanide is present 
in the bath is indicated by the appearance of the silvered objects 
and the properties of the deposit, as well as by the behavior of 
the anodes in the bath during and after silvering. 

It may be accepted, as a rule, that with a moderate current the 
object must, in the course of 10 to 15 minutes, be coated with a 
thin, dull white film of silver. If this be not the case and the 
film of silver shows a meagre bluish-white tone, potassium cyan- 
ide is wanting. However, if, on the other hand, the dull white 
deposit forms within 2 to 3 minutes, and shows a crystalline 
structure, or a dark tone playing into gray-black, the content of 
potassium cyanide in the bath is too large, provided the current 
is not excessively strong. If copper and brass become coated 
with silver without the assistance of the current, the bath con- 
tains also too much potassium cyanide. 

In silvering, even if the objects are to be but thinly coated, in- 
soluble platinum anodes should never be used, but only anodes 
of fine silver, which are capable of keeping the content of silver 
in the bath quite constant. From the behavior and appearance 
of the anodes, a conclusion may also be drawn as to whether the 
content of potassium cyanide in the bath is too large or too small. 
If the anodes remain silver-white during silvering, it is a sure 
sign that the bath contains more potassium cyanide than is 
necessary and desirable; but if they turn gray or blackish, and 
retain this color after silvering when no current is introduced 
into the bath for a quarter of an hour or more, potassium cyanide 
is wanting. On the other hand, the correct content of potassium % 
cyanide is present when the anodes acquire during the silvering 
process a gray tone, which, after the interruption of the current, 
gradually changes back to a pure white. 

Potassium cyanide when found wanting should be quickly 
added, though never more than 30 to 37 J grains per quart of the 



DEPOSITION OF SILVER. 217 

bath at one time, so as to avoid going to the other extreme. Too 
large a content of potassium cyanide is remedied by adding to the 
bath, with constant stirring, a small quantity of cyanide or chlo- 
ride of silver rubbed with water to a thinly fluid paste, whereby 
the excess is rendered harmless in consequence of the formation 
of the double salt of silver and potassium cyanide. Instead of 
such addition, the current may, however, be used as a corrector, 
of the excess. For this purpose suspend as many silver anodes 
as possible to the anode-rods, but only a single anode as an object 
to the object-rod, and allow the current to pass for a few hours 
through the bath, whereby the excess of potassium cyanide is 
rendered innoxious by the dissolving silver. 

The bath can be kept quite constant by silver anodes provided 
potassium cyanide be regularly added at certain intervals, and the 
anode-surface is equal to that of the objects to be silvered. But 
since, on account of the expense, a relatively small anode-surface 
is frequently used, the content of silver in a bath continuously 
worked will finally become lower, and augmentation, by the addi- 
tion of silver, will be required. The manner of effecting this 
augmentation depends on whether the baths are used for silvering 
by weight or for lighter silvering, or whether the baths are worked 
without stopping from morning till evening. If the content of 
silver in baths I. and la. is not to be augmented by the current 
itself, it is best to use exclusively solution of silver cyanide in 
potassium cyanide. If, however, the working of such a bath can 
for some time be interrupted, then add not too small a quantity 
of potassium cyanide to the bath, and, after hanging a small 
silver anode on the object-rod and a sufficient number of anodes 
on the anode-rods, dissolve with not too weak a current silver 
from the anodes until the latter, which at first remain white, 
begin to acquire a gray tone. Silver is, of course, deposited upon 
the anode suspended as an object, which is, however, not lost, it 
being dissolved later on when the anode is secured to the anode- 
rod. The quantity of silver dissolved is considerably larger than 
that deposited upon the small anode-surface suspended as an 
object. 

It has previously been mentioned that with proper treatment 
baths made with chloride of siver have the same duration of life 



218 ELECTRO-DEPOSITION OF METALS. 

as those prepared with cyanide of silver. The chief feature of 
such proper treatment is the augmentation of the content of silver 
by electrolysis, i. e., by the current itself. If it were not possible 
to proceed in this manner, the bath, by the frequently repeated 
additions of solution of the chloride, instead of the cyanide of 
silver, in potassium cyanide, would gradually thicken by reason 
of the potassium chloride which is thereby simultaneously intro- 
duced, and in consequence of this would offer greater resistance 
to the current. The fear expressed by some that a crystalline 
separation of potassium chloride, and the consequent formation of 
a porous deposit upon the objects, might take place is erroneous, 
potassium chloride being one of the most soluble salts and show- 
ing but little tendency to separate in crystals from aqueous solu- 
tions. The above-mentioned gradual thickening is, however, a 
disadvantage, which shows itself by the deposit being less homo- 
geneous, and for this reason it is advisable, when silvering by 
weight, to use silver cyanide instead of the chloride for strength- 
ening the silver bath. 

A gradual thickening of the bath may also take place if potas- 
sium cyanide containing potash is used instead of the preparation 
free from potash, and of 98 to 99 per cent, purity. Even pure 
fused potassium cyanide produces a thickening of the bath, 
which, however, progresses very slowly. This thickening is due 
to a portion of the excess of potassium cyanide being converted 
by the action of the air into potassium carbonate. The latter 
thus formed must from time to time be neutralized, which is 
mostly done with prussic acid, the potassium carbonate being 
thereby converted into potassium cyanide. Instead of prussic 
acid, calcium cyanide or barium cyanide may be added as long 
as a precipitate of calcium carbonate or barium carbonate is 
formed, the clear solution being separated from the precipitate by 
filtering. 

For augmenting the content of silver in baths prepared ac- 
cording to formula II., solution of nitrate of silver or of chloride 
of silver in potassium cyanide may unhesitatingly be used, since 
the thickening proceeds more slowly on account of the smaller 
content of salt in the bath, and because a cheaper bath can be 
more readily renewed without the sacrifice of money than one for 



DEPOSITION OF SILVER. 219 

heavy silvering. The recovery of silver from old baths is effected 
by one of the methods given later on. 

To determine whether the bath contains silver and excess of 
potassium cyanide in proper proportions, the following method 
may be used : Dissolve 1 gramme (15.43 grains) of chemically 
pure crystallized nitrate of silver in 20 grammes (0.7 oz.) of water, 
and gradually add this solution, with constant stirring with a 
glass rod, to 100 grammes (3.52 ozs.) of the silver bath in a 
beaker glass as long as the precipitate of silver cyanide formed 
dissolves by itself. If, after adding the entire quantity of silver 
solution, the precipitate dissolves rapidly, too large an excess of 
potassium cyanide is present in the bath, and vice versa, if the 
precipitate does not completely dissolve after stirring, potassium 
cyanide is wanting. 

While this experiment allows us to judge of the proportion of 
silver to potassium cyanide, it does not throw any light upon the 
i effective content of silver in the bath, and for refreshing the latter, 
it is desirable to know the actual content of silver in it. To de- 
termine this, mix 25 cubic centimetres of the silver bath in a 
beaker glass with 50 cubic centimetres of pure hydrochloric acid 
and 50 cubic centimetres of water, and heat upon a water or sand 
bath until all odor of prussic acid has disappeared, and then dilute 
with 200 cubic centimetres of water. Filter off the precipitate of 
chloride of silver formed through a weighed filter, previously dried 
at 212° F., wash the precipitate with hot distilled water until the 
nitrate is no longer rendered turbid by a drop of silver solution (1 
part of nitrate of silver to 20 of water), and dry at 212° F. until 
the weight remains constant. After deducting the weight of the 
dried filter, the weight of the precipitated chloride of silver is 
obtained, and from this the weight of the metallic silver is calcu- 
lated according to the following formula : — 

143.5 : 108=grammes of cloride of silver found : x. 

The content of silver in the bath per liter is then found by 
multiplying x by 40. 

In silvering, the constant agitation of the layers of fluid is of 
decided advantage, streaks being otherwise readily formed upon 
the silvered objects. To keep the articles in gentle motion while 



220 



ELECTEO-DEPOSITION OF METALS. 



in the bath, one method is to connect the suspending rods to a 
frame of iron having four wheels, about 3 inches in diameter, 
connected to it, which slowly travel to and fro to the extent of 
3 or 4 inches upon inclined rails attached to the upper edges of 
the tank, the motion, which is both horizontal and vertical, being 
given by means of an eccentric wheel driven by steam power. 
By another arrangement, the frame supporting the articles does 
not rest upon the tank, but is suspended above the bath, and 
receives a slow swinging motion from a small eccentric or its 
equivalent. In the Elkington establishment at Birmingham the 
following arrangement is in use : All the suspending rods of the 
bath rest upon a copper mounting, which, by each revolution of 
an eccentric wheel, is lifted about f inch, and then returned to its 
position ; the copper mounting is connected to the main negative 
wire of the dynamo-machine by a copper cable. The same object 
may also be attained by giving the objects a horizontal instead of 
vertical motion, as shown in Fig. 108, in which the motion is 
produced by an eccentric wheel on the side. 

Fig. 108. 




Finally it remains to mention a singular phenomenon in silver- 
ing which has not yet been explained. A small addition of cer- 
tain, and especially of organic, substances, which, however, must 
not be made suddenly or in too large quantities, produces a fuller 



DEPOSITION OF SILYEE. 221 

and better adhering deposit of greater lustre than can be produced 
in fresh baths. Elkington observed that an addition of a few 
drops of carbon disulphide to the bath made the silvering more 
lustrous, while others claim to have used with success solutions of 
iodine in chloroform, of gutta-percha in chloroform, as well as 
heavy hydrocarbons, tar, oils, etc. However, many baths have 
been entirely spoiled by an attempt to change them into bright 
working baths by the addition of such ingredients ; and hence it 
is best to leave such experiments alone. There is no doubt that 
a silver bath becomes better in the degree as it takes up small 
quantities of organic substances from dust and air. Fresh silver 
baths will more rapidly accommodate themselves to regular work- 
ing by the addition of a few drops of spirit of sal ammoniac. 

After silvering the objects frequently show, instead of a pure 
white, a yellow tone or they become yellow in the air, which is 
ascribed to the formation of basic silver salts in the deposit. To 
overcome this evil it has been proposed to allow the objects to 
remain in the bath for a few minutes after interrupting the cur- 
rent, whereby the basic salts are dissolved by the potassium cyan- 
ide of the bath ; or the same object is attained by inverting the 
electrodes for a few seconds, after plating, thus transforming the 
articles into anodes. The electric current carries away the basic 
salt of silver in preference to the metal. This operation should, 
of course, not be prolonged, otherwise the silver will be entirely 
removed from the objects, and will be deposited on the anodes. 
For the same purpose some electro-platers hold in readiness a 
warm solution of potassium cyanide, in which they immerse the 
silvered articles for half a minute. 

Execution of silvering. — A. Silvering by iveight. — Copper, brass, 
and all other copper alloys may be directly silvered after amalga- 
mating (quicking), whilst iron, steel, nickel, zinc, tin, lead, and 
Britannia are first coppered or brassed, and then amalgamated. 

The mechanical and- chemical preparation of the objects for the 
silvering process is the same as described on pages 126 and 131. 
To obtain well-adhering deposits great care must be exercised in 
freeing the objects from grease and in pickling. As a rule, objects 
to be silvered are ground and polished ; but polishing must not be 
carried too far, since the deposit of silver does not adhere well to 
highly polished surfaces ; and in case such highly polished objects 



222 ELECTRO-DEPOSITION OP METALS. 

are to be silvered it is best to deprive them of their smoothness 
by rubbing with pumice powder, emery, etc., or by pickling. 

The treatment of copper and its alloys, German silver and 
brass, which have chiefly to be considered in silvering by weight, 
is, therefore, as follows : — 

1. Freeing from grease by hot potash or soda lye (1 part of 
caustic alkali to 8 or 10 parts of water), or by brushing with the 
lime-paste mentioned on page 132. 

2. Pickling in a mixture of 1 part, by weight, of sulphuric 
acid of QQ° Be. and 10 of water. This pickling is only required 
for rough surfaces of castings, ground articles being immediately 
after freeing from grease treated according to 3. 

3. Rubbing with a piece of cloth dipped in fine pumice powder 
or emery, after which the powder is to be removed by washing. 

4. Pickling in the preliminary pickle, rinsing in hot water, and 
quickly drawing through the bright dipping bath (page 127), and 
again thoroughly rinsing in several waters. 

5. Amalgamating {quicking) by immersion in a solution of mer- 
cury, called the quicking solution, and consisting of a solution of 
0.35 ounce of nitrate of mercury in 1 quart of water, to which, 
with constant stirring, pure nitric acid in small portions is added 
until a clear fluid results ; a weak solution of potassium-mercury 
cyanide in water is, however, preferable for quicking. 

6. In the quicking solution the objects remain only long enough 
to acquire a uniform white coating, when they are rinsed in clean 
water, and gone over with a brush in case the quicking shows a 
gray instead of a white tone. 

The objects are now brought into the silver bath and secured 
to the suspension rods by slinging wires of copper. For forks 
and spoons these wires are bent on their extremities 
Fig. 109. m g^h a maimer that the fork or spoon may readily 
be inserted or removed. Fig. 109 presents this ter- 
minal hook. The straight portion of these wires 
which dips into the liquid is covered with a small 
tube of India rubber or coated with ebonite mass, 
which prevents the useless deposit of silver upon it. 
The hooped portions, however, become coated with 
silver, which may be removed by the use of acids 
after having raised the India-rubber tube. 




DEPOSITION OF SILVER. 223 

Introduce into the bath at first a somewhat more powerful 
current so that the first deposit of silver takes place quite rapidly, 
and after 3 minutes regulate the current so that in 10 to 15 
minutes the objects are coated with a thin, dull film of silver. 
At this stage take them from the bath, and after seeing that all 
portions are uniformly coated with silver, scratch-brush them 
with a brass brush, which should, however, not be too fine. 
In doing this the deposit must not raise up ; if at this stage the 
objects stand thorough scratch-brushing, raising of the deposit in 
burnishing later on need not be feared. 

Any places which show no deposit of silver are vigorously 
scratch-brushed with the use of pulverized tartar, then again 
carefully cleansed by brushing with lime-paste to remove any im- 
purities due to touching with the hands, pickled by dipping in 
potassium-cyanide solution, rinsed off again, quicked, and after 
careful rinsing returned to the bath. Special care must be had 
not to contaminate the bath with quicking solution, as this would 
soon spoil it. 

The objects now remain in the bath until the deposit has ac- 
quired a weight corresponding to the desired thickness. Knives, 
forks, and spoons receive a deposit of 2.11 to 3.52 ozs. of silver 
per dozen, such deposit being produced with elements in 10 to 14 
hours, and with a dynamo-electrical machine in 4 to 5 hours. 
According to Dr. William H. Wahl, the amount of silver de- 
posited upon the several grades of plated table ware manufactured 
by the William Rogers Manufacturing Co., of Hartford, Conn., 
is as follows : — 



Per gross. 


Extra plate. 


Double plate. 


Triple plate. 


Teaspoons . 


48 dwts. 


4 ozs. 


6 ozs. 


Desertspoons and forks 


72 " 


6 " 


9 " 


Tablespoons and med. forks 


96 " 


8 " 


12 " 



In order to control the weight of the deposit proceed as fol- 
lows : After having removed one of the pans of a sensitive beam 
balance, substitute for it a brass rod which keeps the other pan in 
equilibrium. Under this rod place a vessel filled with pure water 
and of sufficient diameter and depth to allow of the article sus- 
pended to the rod dipping entirely into the water without touch- 
ing the sides of the vessel. Suppose now that several dozen 



224 



ELECTRO-DEPOSITION OF METALS. 



spoons of the same size and shape are at the same time to be 
provided with a deposit of a determined weight, it suffices to 
control the weight of the deposit of a single spoon, and when this 
has acquired the necessary deposit all the other spoons will also 
be coated with a deposit of silver of the same thickness as the test 
spoon. After quicking and carefully rinsing the spoons, one 
of them is suspended to the brass rod of the balance so that it 
dips entirely under water ; the equilibrium is then re-established 
by placing lead shot upon the pan of the scale, and adding the 

Fig. 110. 




weight corresponding to the deposit the spoon is to receive. Now 
bring the weighed spoon together with the rest into the bath, and 
proceed with the silvering process in the ordinary manner. After 
some time the weighed spoon is taken from the bath, rinsed in 



DEPOSITION OF SILVER. 



225 



water, and hung to the brass rod of the scale ; if it does not 
restore the equilibrium of the latter, it is returned to the bath, 
after some time again weighed, and so on until its weight corre- 
sponds to that of the lead shot and weight placed in the pan of 
the scale, when it is assumed that the balance of the articles have 
also received their proper quantity and that the operation is com- 
plete. 

A more complete weighing apparatus is the plating balance 
first used by Brandely and later on improved by Roseleur. The 
apparatus, which is shown in Fig. 110, is designed for obtaining 
deposits of silver " without supervision and with constant accu- 
racy, and which spontaneously breaks the current when the 
operation is terminated." It is manufactured in various sizes 
suitable for small or large operations. 

It consists of: 1. A wooden vat, the upper edge of which 
carries a brass winding-rod having a binding screw at one end to 
receive the positive conducting wire of the battery ; from this rod 
the anodes are suspended, which are entirely immersed in the solu- 
tion, and communicate with brass cross rods by 
means of platinum wire hooks. These cross 
rods are flattened at their ends so that they may 
not roll, and at the same time have a better con- 
tact with the " winding-rod." 2. A cast-iron 
column screwed at its base to the side of the 
vat, and which carries near the top two project- 
ing arms of cast-iron, the extremities of which 
are vertical and forked, and may be opened or 
closed by iron clamps. These forks are intended 
for sustaining the beam and preventing the 
knives from leaving their bearings under the 
influence of too violent oscillations. In the 
middle of the two arms are two wedge-shaped 
recesses of polished steel to receive the knife 
edges of the beam. One of the arms of the 
column carries at its end a horizontal ring of iron in which is 
fixed a heavy glass tube supporting a cup of polished iron which 
is insulated from the column (Fig. 111). 

This cup has at its lower part a small pocket of lamb-skin or 

15 




226 ELECTRO-DEPOSITION OF METALS. 

of India rubber, which by means of a screw beneath may be 
raised or lowered. This flexible bottom allows the operator to 
lower or raise at will the level of the mercury introduced after- 
wards into the iron cup. Another lateral screw permits con- 
nection to be made with the negative electrode. 3. A cast-iron 
beam carrying in the middle two sharp knife edges of the best 
steel hardened and polished. At each extremity there are two 
parallel bearings of steel separated by a notch, and intended for 
the knife edges of the scale-pan that receives the weights, and 
those of the frame supporting the articles to be silvered. One of 
the arms of the beam is provided with a stout platinum wire, 
placed immediately above and in the centre of the cup of mercury. 
According as the beam inclines one way or the other, this wire 
plays in or out of the cup. 4. A scale-pan for weights, with two 
knife edges of cast-steel, which is attached to four chains support- 
ing a wooden pan for the reception of weights. A smaller pan 
above is intended for the weights corresponding to that of the 
silver to be deposited. 5. The frame for supporting the articles 
to be silvered, which is also suspended from two steel knife edges, 
and the rod of which is formed of a stout brass tube attached 
below to the brass frame proper, which last is equal in dimen- 
sions to the opening of the vat, and supports the rods to which 
the articles are suspended. 

Fig. 112 shows a Roseleur plating balance, together with the 
resistance board, voltmeter, and silver bath ; and will be under- 
stood without further explanation. 

For calculating the weight of the deposit from the density of 
current, see " Chemical and Electric Equivalents." 

When the articles have received a deposit of the required 
weight, they are treated for the prevention of subsequent yellow- 
ing according to one of the methods given on p. 221, then scratch- 
brushed with the use of decoction of soap-root, plunged in hot 
water, and dried in sawdust. 

Articles which are to retain the beautiful crystalline dead white 
with which they come from the bath are, without touching them 
with the fingers or knocking them against the sides of the vessel, 
plunged into very hot clean water and then suspended free to dry; 
immediately after drying they are to be provided with a thin coat 



DEPOSITION OF SILVER. 



227 



of kristalline or zapon to protect the dead white coating which 
readily turns yellow, and, moreover, is very sensitive. 

The silvered articles having been scratch-brushed, must finally 
be polished, which may be effected upon a fine felt wheel with the 



Fie. 112. 




use of rouge, but imparting high lustre by burnishing is to be 
perferred, the deposit being first treated with the steel burnisher 
and then with the stone burnisher, as explained on p. 124. The 
steel burnisher consists of a piece of polished steel varying in 
shape mounted in a wooden handle. The operation of burnish- 
ing is very simple. Take hold of the tool very near to the steel 
or stone, and lean very hard with it on those parts which are to 
be burnished, causing it to glide by a backward and forward 
movement without taking it from the piece. When it is requisite 
that the hand should pass over a large surface at once, without 



228 ELECTRO-DEPOSITION OE METALS. 

losing its point of support on the work-bench, in taking hold of 
the burnisher be careful to place it just underneath the little finger. 
By these means the work is done more quickly, and the tool is 
more solidly fixed in the hand. During the whole process the 
tool must be continually moistened with soap-suds. 

In some establishments in which plated table-ware in large 
quantity is turned out, ingeniously devised burnishing machines 
driven by power are in use, by which much of the manual labor 
is spared. The knife, spoon, etc., each supported by its tips in a 
suitable holder, are very slowly rotated, while the burnishing tool 
moves quickly over the surface, performing the work rapidly and 
satisfactorily. 

When the burnishing is completed, the surface is wiped off 
longitudinally with an old, soft calico rag ; sawdust, hard cloth, 
and tissue paper produce streaks. 

B. Ordinary silvering. — The operations the objects which are 
to receive a deposit of less thickness have to undergo, are ex- 
actly the same as those described under silvering by weight, the 
only difference being that for quicking a weaker solution (15 to 
31 grains of nitrate of mercury to 1 quart of water) or very dilute 
solution of potassium-mercury cyanide is used, and that the 
objects remain in the bath for a shorter time. As previously 
mentioned, iron, steel, zinc, tin, etc., must previously be coppered 
or brassed; however, tin and its alloys may also be directly 
silvered in the silver bath, but a larger excess of potassium 
cyanide is required than for copper, brass, or German silver. 

According to Dr. William H. Wahl, in the United States, the 
practice of previous coppering is not adopted either with Bri- 
tannia metal or steel. The practice of different establishments of 
cleansing their work differs somewhat, but all aim at the same 
result, viz., to secure a smooth adhering coating of metal upon 
an inferior base. 

The practice of the Meriden Britannia Co.'s works at Mericlen, 
Conn., as 'observed by Dr. William H. Wahl, is substantially as 
follows: With Britannia or "white metal:" The article is first 
cleansed of all grease by immersion in boiling alkali; then into 
dilute muriatic acid; then into a "striking" solution, viz., a weak 
cyanide of silver solution with a large proportion of free cyanide 



DEPOSITION OF SILVER. 229 

of potassium, and a large silver anode operated with a very strong 
electric current. The purpose of immersion in this solution is to 
effect an instantaneous deposit of silver on the metal, to better 
insure a perfect coating in the silver bath proper. The articles 
remain in the " striking" solution for a few seconds only, as its 
action, owing to the large proportion of free cyanide it contains, 
is very prompt, and as soon as they have received a thin coating, 
which takes place almost immediately, they are removed to the 
electro-plating bath, where they remain until they have received 
the proper coating of silver. In many cases, especially with 
articles of considerable size, cleansing in boiling alkali must be 
supplemented by scratch-brushing, in which case the acid dip may 
be dispensed with, and the article, after thorough rinsing and 
dipping in alkali to remove finger-marks, is immersed at once in 
the " striking*' solution. 

German silver or nickel articles are first cleansed in boiling 
alkali, washed, then dipped in a mixture of two-thirds sulphuric 
acid and one-third nitric acid, then into quicking solution, then 
into the "striking" solution, and from this into the plating bath. 

Steel articles are cleansed in boiling alkali, rinsed, dipped in 
muriatic acid, then in the " striking" solution, and from this into 
the plating bath. In case the articles require scouring the acid 
dip is dispensed with. For steel two "striking" solutions are 
used, one somewhat richer in silver than the other, the weaker 
solution being used first. 

With the William Rogers Manufacturing Co., Hartford, Conn., 
the following is the general outline of the methods in use for pre- 
paring work for plating : — 

For cleansing (steel) cutlery. — Immersion in boiling alkali for 
the removal of grease ; scouring ; rinsing ; dipping into strong 
muriatic acid; then for a few seconds in a silver "striking" 
solution ; then in a plating bath until the required amount of 
silver is deposited. 

The formula for the "striking" solution, which will be given 
later on, is low in silver, rich in cyanide, and worked with a strong 
current and silver anode. 

Nickel-silver (German silver) for spoons. — Immerse in boiling 
alkali; scouring, if necessary, rinsing in water; immersion in 



230 ELECTKO-DEPOS1TION OF METALS. 

acid mixture, composed of two-thirds sulphuric acid and one- 
third nitric acid ; dipping in weak quicking solution (either very 
dilute potassium-mercury cyanide or acidulated nitrate of mer- 
cury); immersion for a few seconds in the silver "striking" solu- 
tion ; and from this into the plating bath. 

Britannia metal (hollow-ware). — Cleansing in alkali as above ; 
rinsing in water; again immersing in alkali to remove finger- 
marks, if necessary, immersing in the "striking" solution, and 
from this into the plating solution. A quicking solution for 
Britannia, sometimes employed, is composed of a strong solution 
of sal ammoniac and corrosive sublimate, into which the articles 
are dipped after cleansing in potash. 

The silver " striking" solution, as used by the \Vm. Rogers 
Manufacturing Co., of Hartford, Conn., is composed as follows: — 

Rogers's "striking" solution. — Cyanide of potassium 6 ozs., 
silver \ oz., water 1 gallon. Use a strong current. 

Meriden Company's "striking solution.'" — Cyanide of potassium 
12 to 16 ozs., silver 8 to 10 dwts , water 1 gallon. 

The plating solution commonly employed by the Wm. Rogers 
Manufacturing Co. has the following composition : Cyanide of 
potassium 6 ozs., silver (in chlorate) 4 ozs., water 1 gallon. 

The usual formula of the Meriden Britannia Co. has the fol- 
lowing proportions: Cyanide of potassium 12 ozs., silver 3 ozs., 
water 1 gallon. 

In order to secure an extra heavy coating of silver on the con- 
vex surfaces of spoons and forks, which, being subject to greater 
wear than the other parts, require extra protection, the Meriden 
Britannia Co. uses a frame in which the articles supported therein 
by their tips are placed horizontally in a shallow silver bath, and 
immersed just deep enough to allow the projecting convexities to 
dip into the bath. By this artifice these portions are given a 
second coating of silver of any desired thickness. This mode of 
procedure, which is termed " sectional" plating, accomplishes the 
intended purpose nicely and satisfactorily. . In some establish- 
ments the silvered forks and spoons are placed between plates of 
gutta-percha of corresponding shape, and held together by rubber 
bands. In these plates the portions to be provided with an extra 
coating of silver are cut out. By suspending the forks and spoons 



DEPOSITION OF SILVER. 231 

thus protected in the bath, the unprotected places receive a further 
layer of silver, the outlines of which are later on smoothed down 
with burnishers. 

" Stopping off." — Stopping off is the manipulation by which 
certain parts of a metallic article, which may be already covered 
with an electro-deposit on its whole surface, are coated with an- 
other metal. For instance, if it is desired to gild the parts in relief 
of an object the other portions are "stopped off," and vice versa. 
Stopping off varnish is prepared by dissolving asphalt or dammar 
with an addition of mastic in oil of turpentine. Apply with a 
brush, and after thoroughly drying the articles in the drying cham- 
ber place them for one hour in very cold water, whereby the 
varnish hardens completely. After electro-plating the varnish is 
removed, best with benzine, the article plunged in hot water and 
dried in sawdust. 

For a varnish that will resist the solvent power of the hot alka- 
line gilding liquid, Gore recommends the following composition : 
Translucent rosin 10 parts, yellow beeswax 6, extra-fine red 
sealing-wax 4, finest polishing rouge 3. 

Silvering of iron. — The article to be silvered is first immersed 
in a warm bath of dilute hydrochloric acid, then in a solution of 
mercuric nitrate, and connected with the zinc pole of a Bunsen 
element. The iron becomes rapidly covered with a layer of mer- 
cury. It may then be brought into the silver bath and the re- 
quired quantity of silver deposited on it. By heating to 572° F. 
the mercury separates and the silver adheres firmly to the iron. 
To save silver the iron may also be coated with a layer of tin. 
Dissolve 1 part of purified tartar in 8 parts of boiling water and 
connect one or more tin anodes with the carbon pole of a Bunsen 
element. The zinc pole is connected with a bright copper sheet 
and the current conducted through the bath until the copper is 
coated with a sufficient layer of tin. The copper is then removed 
and replaced by the iron article. Articles thus coated with tin 
and then silvered are cheaper than those produced by any other 
method. 

Silvering by contact, by immersion, and cold silvering with paste. — 
For silvering by contact with zinc the bath prepared according to 
formula II. may be used, adding about 77 grains more of cyanide 



232 ELECTRO-DEPOSITION OF METALS. 

of potassium per quart. The articles are to be prepared in the 
same manner as for silvering by weight and quicked in a weak 
quicking solution. Before placing the articles in the bath they 
are wrapped round with bright zinc wire, or are brought in con- 
tact while in the bath with a bright strip of zinc, care being had 
to frequently change the points of contact to prevent the forma- 
tion of stains. As previously mentioned, by the contact of the 
metal to be silvered with the electro-positive zinc a weak current 
is produced which effects the deposition of the silver, but this 
taking place very slowly it is best to heat the silver bath. Silver 
being at the same time deposited upon the zinc, the latter must be 
frequently freed from the deposit and brightened by means of a 
file or emery paper. 

By contact with zinc silver may also be deposited in one of the 
following baths for silvering by immersion : Crystallized nitrate of 
silver 5.64 drachms, 98 per cent, potassium cyanide 1.23 ozs., 
water 1 quart. To prepare the bath dissolve the silver salt in 
1 pint of distilled water, then the potassium cyanide in the re- 
maining pint of water, and mix the two solutions. The bath is 
heated in a porcelain or enamelled iron vessel to between 176° 
and 194° F., and the thoroughly cleansed and pickled objects 
are immersed in it until uniformly coated ; previous quicking is 
not required. The deposit is lustrous if the articles are left but a 
short time in the bath, but becomes dull when they remain longer ; 
in the first case the deposit is a mere film, and, while it is some- 
what thicker in the latter, it can under no circumstances be called 
solid. 

The bath gradually works less effectively and finally ceases to 
silver, when it may be attempted to restore its action by the addi- 
tion of 2f to 5| drachms of potassium cyanide per quart. Should 
this prove ineffectual, the content of silver is nearly exhausted, and 
the bath is evaporated to dryness, and the residue added to the 
silver waste. Frequent refreshing of the bath with silver salt 
cannot be recommended, the silvering always turning out best in 
a fresh bath. 

A solution of nitrate of silver in sodium sulphide is, according 
to Roseleur, very suitable for silvering by immersion. The solu- 
tion is prepared by pouring into a moderately concentrated solu- 



DEPOSITION OF SILVER. 



233 



tion of sodium sulphide, with constant stirring, solution of a silver 
salt until the precipitate of silver sulphide formed begins to be 
dissolved with difficulty. This bath can be used cold or warm, 
fresh solution of silver being added when it commences to lose its 
effect. If, however, the bath is not capable of dissolving the 
silver sulphide formed, concentrated solution of sodium sulphide 
has to be added. 

For the preparation of the solution of sodium sulphide, Rose- 
leur recommends the following method : — 

Fig. 113. 




Into a tall vessel of glass or porcelain (Fig. 113) introduce 5 
quarts of water and 4 pounds of crystallized soda, after pouring 
in mercury about an inch or so deep to prevent the glass tube 
through which the sulphurous acid is introduced from being 
stopped up by crystals. The sulphurous acid is evolved by heat- 
ing copper turnings with concentrated sulphuric acid, washing the 
gas in a Woulff bottle filled an inch or so deep with water, and 
introducing it into the bottle containing the soda solution, as 
shown in the illustration. A part of the soda becomes trans- 
formed into sodium sulphide, which dissolves, and a part is pre- 
cipitated as carbonate. The latter, however, is transformed into 
sodium sulphide by the continuous action of sulphurous acid, and 
carbonic acid gas escapes with effervescence. When all has be- 



234 ELECTRO-DEPOSITION OF METALS. 

come dissolved the passage of sulphurous acid should be continued 
until the liquid slightly reddens blue litmus-paper, and then 
allowed to stand aside for 24 hours. At the end of that time a 
certain quantity of crystals will be found upon the mercury, and 
the liquid above, more or less colored, constitutes the sodium sul- 
phide of the silvering bath. The liquid sodium sulphide thus pre- 
pared should be stirred with a glass rod to eliminate the carbonic 
acid which may still remain in it. The liquid should then be 
again tested with litmus-paper ; and if the blue color is strongly 
reddened, carbonate of soda is cautiously added, little by little, 
in order to neutralize the excess of sulphurous acid. On the 
other hand, if red litmus-paper becomes blue, too much alkali is 
present, and more sulphurous acid gas must be passed through 
the liquid, which is in the best condition for our work when it 
turns litmus-paper violet or slightly red. The solution should 
mark from 22° to 26° Be., and should not come in contact with 
iron, zinc, tin, or lead. 

As will be seen, this mode of preparing the sodium sulphide 
solution is somewhat troublesome, and it is, therefore, recom- 
mended to proceed as follows : Prepare a saturated solution of 
commercial sodium sulphide; the solution will show an alkaline 
reaction, the commercial salt frequently containing some sodium 
carbonate. To this solution add, with stirring, solution of bisul- 
phite of sodium saturated at 122° F., until blue litmus-paper is 
slightly reddened. Then add to this solution concentrated solu- 
tion of nitrate of silver until the flakes of silver sulphide separated 
begin to dissolve with difficulty. 

The immersion bath, prepared according to one or the other 
method, works well and has the advantage of producing silvering 
of a beautiful lustre, such as is desirable for many cheap articles. 
By allowing the articles to remain for a longer time in the bath, 
the lustrous deposit becomes dull. For the production of a 
lustrous coating the bath should always be used cold. It must 
further be protected, as much as possible, from the light, as 
otherwise gradual decomposition takes place. 

According to Dr. Ebermayer, the composition of a silver bath 
for immersion is as follows: Dissolve 1.12 ounces of nitrate of 
silver in water, and precipitate the solution with caustic potash ; 



DEPOSITION OF SILVER. 235 

then thoroughly wash the precipitated silver oxide, and dissolve 
it in 1 quart of water, which contains 3.52 ounces of potassium 
cyanide in solution ; and finally dilute the whole with 1 quart 
more of water. For silvering, the bath is heated to the boiling- 
point, and the silver withdrawn may be replaced by the addition 
of moist silver oxide as long as complete dissolution takes place. 
When the silvering is no longer beautiful and of a pure white 
color, the bath is useless, and is then evaporated. Experiments 
with a bath prepared according to the above directions were not 
satisfactory, the coating being dull and adhering badly. 

For silvering articles, especially those composed of the various 
alloys of copper, without the use of a current, the following pro- 
cess is recommended in " Edelmetattindustrie :" Dissolve silver in 
nitric acid with the assistance of the sand or water bath, and con- 
vert it into chloride of silver by carefully adding hydrochloric 
acid or common salt solution until, after repeated stirring and 
allowing to settle, no more precipitate is formed. Now let the 
mixture rest, then pour off the supernatant fluid and wash the 
white caseous precipitate until litmus-paper is no longer reddened 
by the wash-water. Keep the chloride of silver thus obtained in 
wide- mouthed black bottles. Now prepare two baths in glazed 
pots as follows: 1. A potassium cyanide bath by dissolving 11£ 
drachms of chloride of silver and 2 ozs. of potassium cyanide in 
about 10 quarts of water and heating the mixture to the boiling- 
point. 2. A salt bath consisting of 10 quarts of water, 11 lbs. of 
common salt, 11 lbs. of cream of tartar, and 4J ozs. of chloride of 
silver. Boil the mixture, with constant stirring, for one hour, 
and when cold pour it into another pot in which it may be kept. 
The articles to be silvered are cleansed by treating them with 
dilute hydrochloric acid. They are next pickled by dipping them 
in nitric acid and finally plunged into a bright-dipping bath con- 
sisting of nitric acid, a small quantity of hydrochloric acid, and a 
trace of lampblack. They are then thoroughly rinsed off, and 
thrown into water containing a small quantity of cream of 
tartar, where they remain until they are to be silvered. The 
water must not be warm and the articles should not remain in it 
too long, otherwise they will tarnish and it would be impossible to 
obtain a pure silvering. The articles thus prepared are first 



236 ELECTRO-DEPOSITION OF METALS. 

brought into the potassium cyanide bath and gently agitated, 
when they become immediately coated with a thin film of silver. 
They are then rinsed and brought into a dilute salt bath, pre- 
pared by adding water to a portion of the salt bath given under 
2 (p. 235), where they remain until they have acquired a gray- 
white or yellowish-white color. They are then rinsed, returned 
to the potassium cyanide bath, again rinsed, and thrown in clean 
water, or dried in sawdust. Each rinsing must be effected in a 
different vessel. The two baths are very lasting and require only 
a periodical addition of potassium cyanide (when the articles on 
being immersed become black, which slowly turns to white) or of 
chloride of silver (when the articles show a yellowish-white color). 
When the dilute salt bath becomes too weak a fresh quantity of 
the salt bath is added by means of a wooden spoon. The potas- 
sium cyanide bath must be shaken every day. During the pro- 
cess of silvering the potassium cyanide bath is to be kept at between 
176° and 194° F., and the salt bath at above 212° F. The 
potassium cyanide bath should only be boiled before use, when 
making a fresh addition of potassium cyanide or chloride of sil- 
ver. The silvering obtained with the use of these baths is pure 
white, cheap, and durable. 

The process of coating with a thin film, or rather coloring with 
silver, small articles such as hooks and eyes, pins, etc., differs 
from the above-described immersion process, which effects the 
silvering in a few seconds, in that the articles require to be boiled 
for a longer time. The process is as follows : Prepare a paste 
from 14.11 drachms of nitrate of silver, precipitated as chloride 
of silver ; 44 ounces of cream of tartar, and a like quantity of 
common salt, by precipitating the solution of the nitrate of silver 
with hydrochloric acid, washing the chloride of silver and mixing 
it with the above-mentioned quantities of cream of tartar and 
common salt, and sufficient water to a paste, which is kept in 
a dark glass vessel to prevent, the chloride of silver from being 
decomposed by the light. Small articles of copper or brass are 
first freed from grease, and pickled. Then heat in an enamelled 
kettle 3 to 5 quarts of rain-water to the boiling-point ; add 2 or 3 
heaping tablespoonfuls of the above-mentioned paste, and bring 
the metallic objects contained in a stoneware sieve into the bath 



DEPOSITION OF SILVER. 237 

and stir them diligently with a rod of glass or wood. Before 
placing a fresh lot of articles in the bath additional silver paste 
must be added. If finally the bath acquires a greenish color, 
caused by dissolved copper, it is no longer suitable for the pur- 
pose, and is then evaporated and added to the silver residues. 

Cold silvering with paste. — In this process, an argentiferous 
paste, composed as given below, is rubbed, by means of the 
thumb, a piece of soft leather or rag, upon the cleansed and 
pickled metallic surface (copper, brass, or other alloys of copper) 
until it is entirely silvered. The paste may also be rubbed in a 
mortar with some water to a uniform thinly fluid mass, and 
applied with a brush to the surface to be silvered. By allowing 
the paste to dry naturally, or with the aid of a gentle heat, the 
silvering appears. The application of the paste by means of a 
brush is chiefly made use of for decorating with silver articles 
thinly gilded by immersion. For articles not gilded, the above- 
mentioned rubbing on of the stiff paste is to be preferred. 

Composition of argentiferous pastes. — I. Silver in the form of 
freshly precipitated chloride of silver *0.35 oz., common salt 
0.35 oz., potash 0.7 oz., whiting 0.52 oz., and water a sufficient 
quantity to form the ingredients into a stiff paste. 

II. Silver in the form of freshly precipitated chloride of silver* 
0.35 oz., potassium cyanide 1.05 oz., sufficient water to dissolve 
these two ingredients to a clear solution, and enough whiting to 
form the whole into a stiff paste. This paste is also excellent 
for polishing tarnished silver ; it is, however, poisonous. 

The following composition, which is not poisonous, does excel- 
lent service : Silver in the form of chloride of silver 0.35 oz., 
cream of tartar 0.7 oz., common salt 0.7 oz., and sufficient water 
to form the mixture of the ingredients into a stiff paste. 

Another composition is as follows : Chloride of silver 1 part, 
pearl-ash 3, common salt 1 J, whiting 1, and sufficient water to 
form a paste. Apply the latter to the metal to be silvered and rub 
with a piece of soft leather. When the metal is silvered, wash in 
water to which a small quantity of washing soda has been added. 

Graining. — In gilding parts of watches, gold is seldom directly 
applied upon the copper; there is generally a preliminary opera- 

* From 0.56 oz. of nitrate of silver. 



238 ELECTRO-DEPOSITION OF METALS. 

tion called graining, by which a grained and slightly dead appear- 
ance is given to the articles. Marks of the file are obliterated by 
rubbing upon a whetstone, and lastly upon an oil-stone. Any 
oil or grease is removed by boiling the parts for a few minutes in 
a solution of 10 parts of caustic soda or potash in 100 of water, 
which should wet them entirely if all the oil has been removed. 
The articles being threaded upon a brass wire, cleanse them rapidly 
in the acid mixture for a bright lustre, and dry them carefully in 
white- wood sawdust. The pieces are fastened upon the even side 
of a block of cork by brass pins with flat heads. The parts are 
then thoroughly rubbed over with a brush entirely free from 
grease, and dipped into a paste of water and very fine pumice- 
stone powder. Move the brush in circles, in order not to rub one 
side more than the other ; thoroughly rinse in cold water, and no 
particle of pumice-stone should remain upon the pieces or the 
cork. Next place the cork and the pieces in a weak mercurial 
solution, composed of water 2J gallons, nitrate or binoxide of 
mercury ^ oz., sulphuric acid \ oz., which slightly whitens the 
copper. The pieces are passed quickly through the solution and 
then rinsed. This operation gives strength to the graining, which 
without it possesses no adherence. 

The following preparations may be used for graining : I. Silver 
in impalpable powder 2 ozs., finely pulverized cream of tartar 
20 ozs., common salt 4 lbs. II. Silver powder 1 oz., cream of 
tartar 4 to 5 ozs., common salt 13 ozs. III. Silver powder, 
common salt, and cream of tartar, equal parts by weight of each. 
The mixture of the three ingredients must be thorough and effected 
at a moderate and protracted heat. The graining is the coarser 
the more common salt there is in the mixture, and it is the finer 
and more condensed as the proportion of cream of tartar is 
greater, but it is then more difficult to scratch-brush. The 
silver powder is obtained as follows : Dissolve in a glass or por- 
celain vessel § oz. of crystallized nitrate of silver in 2J gallons 
of distilled water, and place 5 or 6 ribbands of cleansed copper, 
| inch wide, in the solution. These ribbands should be long 
enough to allow of a portion of them being above the liquid. 
The whole is kept in a dark place, and from time to time stirred 
with the copper ribbands. This motion is sufficient to loosen the 



DEPOSITION OF SILVER. 239 

deposited silver, and present fresh surfaces to the action of the 
liquor. When no more silver deposits on the copper the opera- 
tion is complete, and there remains a blue solution of nitrate of 
copper. The silver powder is washed by decantation or upon a 
filter until there remains nothing of the copper solution. 

For the purpose of graining, a thin paste is made of one of the 
above mixtures and water, and spread by means of a spatula 
upon the watch parts held upon the cork. The cork itself is 
placed upon an earthenware dish, to which a rotating movement 
is imparted by the left hand. An oval brush with close bristles, 
held in the right hand, rubs the watch parts in every direction, 
but always with a rotatory motion. A new quantity of paste is 
added two or three times and rubbed in the manner indicated. 
The more the brush and cork are turned the rounder becomes 
the grain, which is a good quality, and the more paste added the 
larger the grain. When the desired grain is obtained the pieces 
are washed and scratch-brushed. The brushes employed are of 
brass wire, as fine as hair and very stiff and springy. It is neces- 
sary to anneal them upon an even fire to different degrees ; one 
soft or half-annealed for the first operation or uncovering the 
grain ; one harder for bringing up the lustre ; and one very soft 
or fully annealed, used before gilding for removing any marks 
which may have been made by the preceding tool, and for scratch- 
brushing after gilding, which, like the graining, must be done by 
giving a rotatory motion to the tool. If it happens that the 
same watch part is composed of copper and steel, the latter metal 
requires to be preserved against the action of the cleansing acids 
and of the graining mixture by a composition called resist. This 
consists in covering the pinions and other steel parts with a fatty 
composition which is sufficiently hard to resist the tearing action 
of the bristle and wire brushes, and insoluble in the alkalies of 
the gilding bath. A good composition is : Yellow wax 2 parts 
by weight, translucent rosin 3 J, extra fine red sealing-wax 1J, 
polishing rouge 1. Melt the rosin and sealing-wax in a porce- 
lain dish, upon a water-bath, and afterwards add the yellow wax. 
When the whole is thoroughly fluid, gradually add the rouge and 
stir with a wooden or glass rod. Withdraw the heat but continue 
the stirring until the mixture becomes solid, otherwise all the 



240 ELECTRO-DEPOSITION OF METALS. 

rouge will fall to the bottom. The flat parts to receive this resist 
are slightly heated and then covered with the mixture, which melts 
and is easily spread. For covering steel pinions employ a small 
gouge of copper or brass fixed to a wooden handle. The metallic 
part of the gouge is heated upon an alcohol lamp, and a small 
quantity of resist is taken with it. The composition soon melts, 
and by turning the tool around the steel pinion thus becomes 
coated. Use a scratch-brush with long wires, as their flexibility 
prevents the removal of the composition. When the resist is to 
be removed after gilding, put the parts into warm oil or tepid tur- 
pentine, then into a very hot soap-water or alkaline solution ; and, 
lastly, into fresh water. Scratch-brush and dry in warm, white 
wood sawdust. The holes of the pinions are cleansed and polished 
with small pieces of very white, soft wood, the friction of which 
is sufficient to restore the primitive lustre. The gilding of parts 
of copper and steel requires the greatest care, as the slightest rust 
destroys their future usefulness. Should some gold deposit upon 
the steel, it should be removed by rubbing with a piece of wood 
and impalpable pumice dust, tin-putty, or rouge. 

The gilding of the grained watch parts is effected in a bath 
prepared according to formula I. or III., given under "Deposition 
of Gold." 

The silvering of fine copper wire is effected in an apparatus 
similar to that shown on page 179, a reservoir containing potas- 
sium cyanide solution for pickling the cleansed wire being added 
and placed in front of the silver bath. Lustre is imparted to the 
silvered wire by drawing through a draw-plate. Further details 
will be given under " Gilding." 

Incrustations with silver, gold, and other metals. — By incru sting 
is understood the inlaying of depressions, produced by engraving 
or etching upon a metallic body, with silver, gold, and other metals, 
such as Japanese incrustations, which are made by mechanically 
pressing the silver or gold into the depressions. Such incrusta- 
tions, however, can also be produced by electro-deposition, the 
process being as follows : The design which is to be incrusted 
upon a metal is executed with a pigment of white-lead and glue- 
water or gum-water. The portion not covered by the design is 
then coated with stopping-off varnish. The article is next placed 



DEPOSITION OF SILVER. 241 

in dilute nitric acid, whereby the pigment is first dissolved, and 
next the surface etched, which is allowed to progress to a certain 
depth. Etching being finished, the article is washed in an abun- 
dance of water and immediately brought into a silver or gold bath, 
in which by the action of the current the exposed places are filled 
up with metal. This being done, the "stopping-off" varnish is 
removed with benzine, the surface ground smooth and polished. 
In this manner one article may be incrusted with several metals ; 
for instance, brass may be incrusted with copper, silver, and gold, 
and by oxidizing or coloring portions of the copper beautiful 
effects can be produced. The principal requisites for these in- 
crustations are manual skill and much patience ; expensive appa- 
ratus is not required, every skilled electro-plater being able to 
execute the work. 

Niel or nielled silvering. — By nielling is understood the inlaying 
of designs, produced either by engraving or stamping, with a 
black mixture of metallic sulphides. For preparing the nielling 
composition a certain proportion of sulphur is introduced into a 
stoneware retort or a deep crucible. A mixture of silver, copper, 
and lead is heated in another crucible, and when melted is poured 
into the fused sulphur, which transforms these metals into sul- 
phides. A small portion of sal ammoniac is then added, and, 
after being removed from the crucible or retort, the product is 
pulverized and is then ready for use. 

The proportions generally used are as follows : — 

Parts. 

- „^ 

Silver 8 2 1 1 

Copper 18 5 6 2 

Lead 13 7 10 4 

Sulphur 9(5 24 36 5 

The firm of Zachers, of Berlin, claim to have discovered the 
process of making the niel called Tula, after the Russian town of 
the same name. According to them, the niel is prepared from 
silver 9 parts, copper 1, lead 1, and bismuth 1. The metals are 
fused and saturated with sulphur. This mixture gives the splendid 
blue which was formerly erroneously considered as steel blue. 

The article to be nielled having been prepared with the graver, 
by etching or stamping, is then covered — hollows and reliefs, with 
16 



242 ELECTRO-DEPOSITION OF METALS. 

the pulverized nielling composition made into a stiff paste with 
solution of sal ammoniac. The article is next heated in the 
muffle until the composition melts, when it will be found to 
adhere firmly to the metal. The design is brought out in very 
effective contrast by denuding the portions in relief, without 
touching the hollows, which retain a fine black. 

To imitate niel by electro-deposition, the design is executed 
upon the surface with a pigment consisting of white lead and glue 
or gum-water. The portions which are to remain free are coated 
with " stopping-off" varnish, and the design is uncovered by 
etching with very dilute nitric acid. The article is then brought 
as the anode into dilute solution of ammonium sulphide, while a 
small sheet of platinum connected to the negative pole is dipped 
into the solution. Sulphide of silver being formed, the design 
becomes quickly black-gray, and, after removing the " stopping- 
off" varnish with benzine, stands out in sharp contrast from the 
white silver. 

Old (antique) silvering. — To give silvered articles an antique 
appearance coat them with a thin paste of 6 parts graphite, 1 red 
ochre, and sufficient spirits of turpentine. After drying, a gentle 
rubbing with a soft brush removes the excess of powder, and the 
reliefs are set off (discharged) by means of a rag dipped into 
alcohol. 

A tone resembling antique silvering is also obtained by brush- 
ing the silvered articles with a soft brush moistened with very 
dilate alcoholic solution of chloride of platinum. 

In order to impart the old silver tinge to small articles, such 
as buttons, rings, etc., they are agitated in the above mentioned 
paste, and then " tumbled" with a large quantity of dry sawdust 
until the desired shade is obtained. 

Many operators, at the present day, produce the antique silver- 
ing by beginning with the oxidizing process about to be described, 
and setting off the reliefs by means of a hard brush and pumice- 
stone, or Spanish white. This last process is almost exclusively 
used for metallic mountings of books and albums. 

Oxidized silver. — This term is incorrect, as by it is understood 
not an oxidation, but a combination with sulphur or chlorine. 
Solution of pentasulphide of potassium (liver of sulphur of the 



DEPOSITION OF SILVER. 243 

shops) is generally used for the purpose. Immerse the articles in 
a solution of 2.75 drachms of liver of sulphur aud 5| drachms 
of ammonium carbonate in 1 quart of water heated to 176° F., 
and allow them to remain until they have acquired the desired 
dark tone. Immediately after immersion the articles become 
pale gray, then darker, and, finally, deep black-blue. For color- 
ing in this manner the silvering should not be too thin ; for arti- 
cles with a very thick deposit of silver, solution of double the 
strength may be used. Very slightly silvered articles cannot be 
oxidized in this manner, as the bath would remove the silvering, 
or under the most favorable circumstances produce only a gray 
color. If the operation is not successful, and the articles come 
from the bath stained or otherwise defective, dip them in a warm 
potassium cyanide solution which rapidly dissolves the silver sul- 
phide formed. 

A yellow color is imparted to silvered articles by immersion in 
a hot concentrated solution of chloride of copper, rinsing and 
drying. 

Stripping silvered articles. — When a silvering operation has 
failed, or the silver is to be stripped from old silvered articles, dif- 
ferent methods have to be used according to the nature of the basis- 
metal. Silvered iron articles are treated as the anode in potas- 
sium cyanide solution in water (.1 : 20), the iron not being brought 
into solution by potassium cyanide. As cathode suspend in the 
solution a few silver anodes or a copper sheet rubbed with an oily 
rag ; the silver precipitates upon the copper sheet, but does not 
adhere to it. Articles, the basis of which is copper, are best 
stripped by immersion in a mixture of equal parts of anhydrous 
(fuming) sulphuric acid and nitric acid of 40° Be. This mixture 
makes the copper passive, it not being attacked while the silver 
is dissolved. Care must, however, be had not to introduce any 
water into the acids, nor to let them stand without being hermeti- 
cally closed, since by absorbing moisture from the air they become 
dilute and may then exert a dissolving effect upon the copper. 
The fuming sulphuric acid may also be heated in a shallow pan 
of enamelled cast-iron to between 300° and 400° F. Then at 
the moment of using it, pinches of dry and pulverized nitrate of 
potassium (saltpetre) are thrown into it, and the article, held with 



244 ELECTBO-DEPOSITION OF METALS. 

copper tongs, is plunged into the liquid. The silver is rapidly 
removed, while the copper or its alloys is but slightly corroded. 
According to the rapidity of the solution, fresh additions of salt- 
petre are made. All the silver has been dissolved when, after 
rinsing in water and dipping the articles into the cleansing acids, 
they present no brown or black spots, that is to say, when they 
behave like new. In this hot acid stripping proceeds more quickly 
than in the cold acid mixture, but the latter acts more uniformly. 

Determination of electro-deposited silvering. — By applying a 
drop of nitric acid of 1.2 specific gravity, in which red chromate 
of potash has been dissolved to saturation, to genuine silvering a 
red stain of chromate of silver is formed. According to Grager, 
this method may also be used, to a certain extent, for the recog- 
nition of other white metals which may be mistaken for silver. 
A drop of the mixture applied to German silver becomes brown, 
no red stain appearing after rinsing with water ; upon Britannia 
the drop produces a black stain ; zinc is etched without a colored 
spot remaining behind ; upon amalgamated metals a brownish 
precipitate is formed, which does not adhere and is washed away 
by water ; upon tin the drop also acquires a brownish color, and 
by diluting with water a yellow precipitate is formed ; upon lead 
a beautiful yellow precipitate is formed. 

Custom-house officers in Germany are directed by law to use 
the following process for the determination of genuine silvering : 
Wash a place on the article with ether or alcohol, dry with blot- 
ting paper and apply to the spot thus cleansed a drop of a 1 to 2 
per cent, solution of crystallized bisulphide of soda prepared 
by boiling 1.05 ozs. of sodium sulphite and 2.36 drachms of 
flowers of sulphur with 0.88 oz. of water until the sulphur is 
dissolved, and diluting to 1 quart of fluid. Allow the drop to 
remain about ten minutes upon the article and then rinse off with 
water. Upon silver articles a full, round, steel-gray spot is pro- 
duced. Other white metals and alloys, with the exception of 
amalgamated copper, do not show this phenomenon, there appear- 
ing at the utmost a dark ring at the edge of the drop. Amalga- 
mated copper is more quickly colored and acquires a more dead 
black color than silver. 



DEPOSITION OF SILVER. 245 

Recovery of silver from old silver baths, etc. — Old solutions 
which contain silver in the form of a silver salt are easily treated. 
It is sufficient to add to them, in excess, a solution of common 
salt, or hydrochloric acid, when all the silver will be precipitated 
in the state of chloride of silver, which, after washing, may be 
employed for the preparation of new baths. 

For the recovery of silver from solutions which contain it as 
cyanide, the solutions may be evaporated to dryness, the residue 
mixed with a small quantity of calcined soda and potassium 
cyanide, and fused in a crucible, whereby metallic silver is 
formed, which, when the heat is sufficiently increased, will be 
found as a button upon the bottom of the crucible ; or if it is not 
desirable to heat to the melting-point of silver, the fritted mass is 
dissolved in hot water, and the solution containing the soda and 
cyanide quickly filtered off from the metallic silver. The evapo- 
ration of large quantities of fluid, to be sure, is inconvenient, and 
requires considerable time. But the reducing process above de- 
scribed is without doubt the most simple and least injurious. 

According to the wet method the bath is strongly acidulated 
with hydrochloric acid, provision being made for the effectual 
carryiug off of the hydrocyanic acid liberated. Remove the 
precipitated chloride of silver and cyanide of copper by filtration, 
and, after thorough washing, transfer it to a porcelain dish and 
treat it, with the aid of heat, with hot hydrochloric acid, which 
will dissolve the cyanide of copper. The resulting chloride of 
silver is then reduced to the metallic state by mixing it with four 
times its weight of crystallized carbonate of soda and half its 
weight of pulverized charcoal. The whole is made into a homo- 
geneous paste, which is thoroughly dried, and then introduced 
into a strongly heated crucible. When all the material has been 
introduced the heat is raised to promote complete fusion and to 
facilitate the collection of the separate globules of silver into a 
single button at the bottom of the crucible, where it will be found 
after cooling. If granulated silver is wanted, pour the metal in a 
thin stream and from a certain height into a large volume of 
water. 

Still simpler is the reduction of the chloride of silver by pure 
zinc ; for this purpose suspend the chloride of silver in water, 



246 ELECTRO-DEPOSITION OF METALS. 

add hydrochloric acid, and place pure zinc rods or granulated 
zinc in the fluid. The zinc dissolving, metallic silver is separated, 
which is filtered off, washed, and dried. 

To precipitate the silver from silver solutions containing potas- 
sium cyanide it suffices to place a bright sheet of zinc in the 
solution, though the simultaneous use of a sheet of zinc and a 
sheet of iron is more suitable. While with the use of zinc alone 
the silver sometimes adheres firmly to the zinc, it always sepa- 
rates in a pulverulent form when zinc and iron are employed. 
It is only necessary to wash the separated silver, which, as a rule, 
contains copper, and after drying to dissolve it, best in warm con- 
centrated sulphuric acid. The solution is diluted with water and 
the dissolved silver precipitated by means of strips of copper. 
The silver thus obtained is perfectly pure. If the content of 
copper is small, it may be removed from the silver precipitated 
with zinc by fusing with a small quantity of saltpetre and borax. 



CHAPTER X. 

DEPOSITION OF GOLD. 



Gold is chiefly found in the metallic state, and generally alloyed 
with more or less silver, copper, and iron. The following analyses 
will serve to show the general composition of the native metal : — 



Australia. California. Russia. Wales. 



Gold 


. 94.64 


89.10 


98.96 


89.83 


Silver 


. 4.95 


10.50 


0.16 


9.24 


Copper . 






0.05 


... 


Iron 


. 0.41 


0.20 


0.35 





100.00 99.80 99.52 99.07 

Gold is one of the few metals possessing a yellow color; pre- 
cipitated from its solution with green vitriol or oxalic acid, it 
appears as a brown powder without lustre, which on pressing 
with the burnisher acquires the color and lustre of fused gold. 
Pure gold is nearly as soft as lead, but possesses considerable 
tenacity. In order to increase its hardness when used for articles 



DEPOSITION OF GOLD. 247 

of jewelry and for coinage it is mixed with silver or copper. The 
" fineness of gold," or its proportion in the alloy, is usually ex- 
pressed by stating the number of carats present in 24 carats of the 
mixture. Pure gold is stated to be 24 carats " fine ;" standard gold 
is 22 carats " fine ;" 18 carat gold is a mixtureof 18 partsof gold and 
6 of alloy. Gold is the most malleable and ductile of the metals ; 
it may be beaten out into leaves not exceeding To-.-jy-orth of a 
millimeter in thickness. When beaten out into thin leaves and 
viewed by transmitted light gold appears green ; when very finely 
divided it is dark red or black. The specific gravity of fused 
gold is 19.35, and of precipitated gold powder from 19.8 to 20.2. 
Pure gold melts at about 2016° F., and in fusing exhibits a sea- 
green color. The melting-points of alloyed gold vary according 
to the degree of fineness. Thus, 23 carat gold melts at 2012° F. ; 
22 carat at 2009° ; 20 carat at 2002° ; 18 carat at 1995° ; 15 
carat at 1992° ; 13 carat at 1990° ; 12 carat at 1987° • 10 carat 
at 1982° ; 9 carat at 1979° ; 8 carat at 1 973° ; 7 carat at 1960°. 
The fineness of gold may be approximately estimated by means 
of the touch-stone, a balsatic stone formerly obtained from Asia 
Minor, but now procured from Saxony and Bohemia. The sam- 
ple of gold to be tested is drawn across the stone, and the streak 
of metal is treated with dilute nitric acid ; from the rapidity of 
the action and the intensity of the green color produced — due to 
the solution of the copper — as compared with streaks made by 
alloys of known composition, the assayer is enabled to judge of 
the proportion of inferior metal which is present. Gold pre- 
serves its lustre in the air and is not acted upon by any of the 
ordinary acids. Nitric, hydrochloric, or sulphuric acid by itself 
does not dissolve gold, but it dissolves in acid mixtures which 
develop chlorine, hence in aqua regia (nitrohydrochloric acid). 

Gold baths. — Electro-gilding may be done with the aid of heat 
or in the cold, large objects being generally gilded in the cold 
bath, and smaller objects in the hot bath. The latter has the 
advantage of requiring less current-strength, besides yielding de- 
posits of greater density and uniformity and of sadder, richer 
tones. Baths for hot gilding work with a moderate content of 
gold — 11^ to 12 J grains of gold per quart — while baths for cold 
gilding should contain not less than 54 grains per quart. 



248 ELECTRO-DEPOSITION OF METALS. 

Some authors — for instance, Eisner, Briant, Selm, and others — 
give the preference to baths prepared with potassium ferrocyanide ; 
while others, like Elkington and Regnault, work with a solution 
of gold-salt and potassium bicarbonate ; and Bottcher, Leuchten- 
berg, and others recommend a solution of cyanide of gold in 
potassium cyanide. With proper treatment of the bath, good 
results may be obtained with either. However, the use of baths 
prepared with potassium ferrocyanide cannot be recommended 
on account of the secondary decompositions which take place 
during the operation of plating, and because the baths do not 
dissolve the gold anodes. In the following, only approved for- 
mulae for the preparation of gold baths will be given : — 

I. Bath for cold gilding. — Fine gold in the form of fulminating 
gold 54 grains, 98 per cent, potassium cyanide 0.35 to 0.5 oz. 
(according to the current-tension used), water 1 quart. 

To prepare this bath, dissolve 54 grains of fine gold in aqua 
regia in a porcelain dish heated over a gas or alcohol flame, and 
evaporate the solution to dryness. Continue the heating until 
the solution is thickly fluid and dark brown and on cooling con- 
geals to a dark brown, foliated mass. Heating too strongly should 
be avoided, as this would cause decomposition and the auric chlo- 
ride would be converted into aurous chloride, and eventually into 
metallic gold and escaping chlorine. The neutral chloride of gold 
prepared in this manner is dissolved in 1 pint of water and aqua 
ammonia added to the solution as long as a yellow-brown pre- 
cipitate is formed, avoiding, however, a considerable excess of 
aqua ammonia. The precipitate of fulminating gold is filtered 
off, washed, and dissolved in 1 quart of water containing 0.5 oz. 
of potassium cyanide in solution. The solution is boiled, re- 
placing the water lost by evaporation, until the odor of ammonia 
Avhich is liberated by dissolving the fulminating gold in potassium 
cyanide disappears when it is filtered. Instead of dissolving the 
gold and preparing neutral chloride of gold by evaporating, it is 
more convenient to use 108 grains of chemically pure neutral 
chloride of gold as furnished by chemical works, and precipitate 
the fulminating gold from its solution. 

Too large an excess of potassium cyanide yields gold deposits 
of an ugly, pale color. When working with a more powerful 



DEPOSITION OF GOLD. 249 

current, the excess of potassium cyanide need only be slight ; 
with a weaker current it must be larger. With 10 per cent. 
excess of free potassium cyanide, the most suitable current- 
strength is 3 volts. 

The fulminating gold should not be dried, as in this condition 
it is highly explosive, but should be immediately dissolved while 
in a moist state. 

For cold gilding, Roseleur recommends the following bath : 
II. Fine gold as neutral chloride of gold 0.35 oz., 98 per cent, 
potassium cyanide 0.7 oz., water 1 quart. 

Dissolve the gold-salt from 0.35 oz. of fine gold or about 0.7 
oz. of neutral chloride of gold in \ pint of water, and the potas- 
sium cyanide in 1 \ pints of water, and after mixing the solutions 
boil for half an hour. The preparation of this bath is more 
simple than that of formula I., but the color of the gold deposit 
obtained with the latter is warmer and sadder than with the 
first. The high content of gold in the bath, prepared according 
to formula II., readily causes a red-brown gold deposit, and hence 
special attention has to be paid to the regulation of the current. 

For those who prefer gold baths prepared with yellow prussiate 
of potash instead of potassium cyanide, the following formula 
for cold gilding is given : — 

III. Yellow prussiate of potash (potassium ferrocyanide) 0.5 
oz., carbonate of soda 0.5 oz., fine gold (as chloride of gold or 
fulminating gold) 30.75 grains, water 1 quart. 

To prepare the bath, heat the solutions of the yellow prussiate 
of potash and of the carbonate of soda in the water to the boiling- 
point, add the gold-salt, and boil \ hour, or with the use of 
freshly precipitated fulminating gold, until the odor of ammonia 
disappears. After cooling, the solution is mixed with a quantity 
of distilled water corresponding to the water lost by evaporation, 
and filtered. This bath gives a beautiful bright gilding upon all 
metals, even upon iron and steel. Suitable current-strength 3.25 
to 3.26 volts. 

Gold, bath for hot gilding. — IV. Fine gold (as fulminating gold) 
15.4 grains, 98 per cent, potassium cyanide 77 grains, water 1 
quart. 

This bath is prepared in the same manner as that according to 



250 ELECTRO-DEPOSITION OF METALS. 

formula I., from 15.4 grains of fine gold, which is converted into 
neutral chloride of gold by dissolving in aqua regia and evapo- 
rating; or dissolve directly 29.32 to 30.75 grains of chemically 
pure neutral chloride of gold in water, precipitate the gold as 
fulminating gold with aqua ammonia, wash the precipitate, dis- 
solve it in water containing the potassium cyanide, and heat until 
the odor of ammonia disappears, replacing the water lost by 
evaporation. This bath yields a beautiful sad gilding of great 
warmth. All that has been said in regard to the content of 
potassium cyanide in the bath prepared according to formula I. 
also applies to this bath. The temperature should be between 
158° and 176° F., and the current-strength 2.0 to 2.5 volts. 

Roseleur recommends for hot gilding : V. Chemically pure 
crystallized sodium phosphate 2.11 ozs., neutral sodium sulphide 
0.35 oz., potassium cyanide 30.86 grains, fine gold (as chloride) 
15.43 grains, distilled water 1 quart. 

If this bath is to serve for the direct gilding of steel, only 15.43 
instead of 30.86 grains of potassium cyanide are to be used. 
Dissolve in a porcelain dish, with the aid of moderate heat, the 
sodium phosphate and sodium sulphide, and when the solution is 
cold, add the nentral chloride of gold prepared from 15.43 grains 
of gold = about 30.86 grains of commercial chloride of gold, and 
the potassium cyanide; for use, heat the bath to between 158° 
and 167° F. 

Conrad Taucher recommends the following formulse for hot 
gilding : — 

VI. Sodium phosphate 14 ozs., sodium bisulphite 3J ozs., 
sodium bicarbonate If ozs., caustic potash If ozs., potassium 
cyanide 14 drachms, gold in the form of neutral chloride 8 J 
drachms, distilled water 10 quarts. 

With the exception of the chloride of gold all the salts may 
be dissolved together. The solution, if necessary, is filtered and 
the gold solution added. The bath is used at between 122° and 
140° F. It yields a very beautiful gilding, but requires a quite 
strong current for its decomposition. It is not suitable for the 
direct gilding of steel. 

VII. Yellow prussiate of potash (potassium ferrocyanide) 54; 



DEPOSITION OF GOLD. 251 

ozs,, pure potassium carbonate If ozs., sal ammoniac 11 \ drachms, 
gold in the form of neutral chloride 5| drachms, water 5 quarts. 

Dissolve with the assistance of heat the first three salts, filter, 
and when cold add the chloride of gold. Then heat again and 
boil for half an hour, replacing the water lost by evaporation. 

Many electro-platers prepare the gold baths with the assistance 
of the electric current. For this purpose prepare a solution of 
3.52 ozs. of potassium cyanide (98 to 99 per cent.) per quart of 
water, and after heating to between 122° and 140° F. conduct 
the current of two Bunsen elements through two sheets of gold, 
not too small, which are suspended as electrodes in the potassium 
cyanide solution. The action of the current is interrupted when 
the solution is so far saturated with gold that an article immersed 
in it and connected to the negative pole in place of the other gold 
sheet is gilded with a beautiful warm tone. By weighing the 
sheet of gold serving as anode, the amount of gold which has 
passed into the solution is ascertained. According to English 
authorities, a good gold bath prepared according to this method 
should contain 3.52 ozs. of potassium cyanide and 0.7 oz. of fine 
gold per quart of water. 

The only advantage of this mode of preparing the bath is that 
it excludes a possible loss of gold which may occur in dissolving 
gold, evaporating the gold solution, etc., by breaking the vessel 
containing the solution. However, by using commercial chemically 
pure chloride of gold such loss is avoided, and the bath prepared 
according to the formulae given yields richer tones than a gold bath 
produced by electrolysis. Besides, the preparation of the gold 
bath with the assistance of the electric current can only be con- 
sidered for smaller baths, since the saturation of a larger volume 
of potassium cyanide solution requires considerable time, and the 
potassium cyanide is strongly decomposed by long heating. 

Management of gold baths. — It is advisable to keep the content 
of gold in the baths prepared according to the different formula? 
as constant as possible, which is best effected by the use of fine 
gold anodes. Insoluble platinum anodes are more liked in gild- 
ing than for all other electro-plating processes, partly because 
they are cheaper, and partly because they are recommended in 
most books on the subject. However, a bath which has become 



252 ELECTRO-DEPOSITION OF METALS. 

low in gold does not yield a beautiful gold color, and has to be 
frequently strengthened by the addition of chloride of gold, the 
preparation of which consumes time and causes expense, so that 
the use of gold anodes is the cheapest in the end. The employ- 
ment of anodes of platinum strips or platinum wire may, per- 
haps, be advocated for coloring the deposit, i. e., for the purpose 
of obtaining certain tones of color when gilding in the hot bath. 
By allowing the platinum anode to dip only slightly in the bath 
a pale gilding is obtained, because the current thereby becomes 
weaker; by immersing the anode deeper the color becomes more 
yellow, and by immersing it entirely the tone becomes more red- 
dish. However, instead of producing these effects of the cur- 
rent-strength by the anode, which requires the constant presence 
of the operator, it is better to obtain the coloration by means of 
the resistance board. By placing the handle upon "strong" a 
reddish gold tone is obtained, and by placing it upon " weak" a 
paler gold tone, while the beautiful gold yellow lies in the middle 
between the two extremes. However, since even with the use of 
gold anodes the content of gold in the bath is not entirely re- 
stored, the bath has after some time to be strengthened, which is 
effected by a solution of fulminating gold or chloride of gold in 
potassium cyanide, according to the composition of the bath. 

As in the silvering baths, the excess of potassium cyanide in 
the gold baths is also partially converted into potassium carbo- 
nate by the action of the air, the heat, etc., and it is, therefore, ad- 
visable from time to time to add a small quantity of potassium 
cyanide. 

Gold baths for cold gilding are kept in vats of stoneware or 
enamelled iron, or small baths, in glass vats, which, to protect 
them against breaking, are placed in a wooden box. Baths for 
hot gilding require enamelled iron vats in which they can be 
heated by a direct fire, or better, by placing in hot water (water 
bath), or by steam. For small gold baths for hot gilding, a 
porcelain dish resting upon a short-legged iron tripod may be 
used. (Fig. 114.) Beneath the iron tripod is a gas burner sup- 
plied with gas by means of flexible India-rubber tubing con- 
nected to an ordinary gas burner. Across the porcelain dish are 
placed two glass rods around which the pole-w r ires are wrapped. 



DEPOSITION OF GOLD. 



253 



In heating larger baths in enamelled vats over a direct fire it may 
happen that on the places most exposed to the heat the enamel 
may blister and peel off; it is, therefore, better to heat the baths 
in a water or steam bath. For this purpose have made a box of 



Fie. 114. 




stout iron or zinc sheet and about f inch wider and longer, and 
about 4 inches deeper than the enamelled vat containing the gold 
bath. To keep the level of the water constant the box is to be 
provided with a water inlet and overflow pipe. In this box place 
the vat so that its edges rest upon those of the box and make the 
joints tight with tow. The water-bath is then heated over a gas 
flame or upon a hearth, the water lost by evaporation being con- 
stantly replaced, so that the enamelled vat is always to half its 
height surrounded by hot water. For heating by steam the 
arrangement is the same, only a valve for the introduction and 
a pipe for the discharge of steam are substituted for the water 
inlet and overflow pipe. 

Execution of gilding, — Like all other electro-plating operations, 
it is advisable to execute gilding with an external source of cur- 
rent; that is, to use a battery or other source of current separated 
from the bath, and to couple the apparatuses as previously de- 
scribed and illustrated by Figs. 47 and 50. 

To be sure, there are still gilders who gild without a battery or 
separate external source of current and obtain good results, the 



254 ELECTRO-DEPOSITION OF METALS. 

process being, as a rule, employed only in gilding small articles. 
The apparatus used for this purpose consists of a glass vessel 
containing the gold solution compounded with a large excess of 
potassium cyanide and a porous clay cell filled with very dilute 
sulphuric acid or common salt solution, which is placed in the 
glass vessel; care should be taken to have the fluids in both ves- 
sels at the same level. Immerse in the clay cell an amalgamated 
zinc cylinder or zinc plate, to which a copper wire is soldered. 
Outside the cell this copper wire is bent downwards, and the arti- 
cle to be gilded, which dips in the gold solution, is fastened to it. 
In working with this apparatus there is always a loss of gold, 
since the gold solution penetrates through the porous cell, and on 
coming in contact with the zinc is reduced by it, the gold being 
separated as black powder upon the zinc. In cleaning the appa- 
ratus this black slime has to be carefully collected and worked for 
fine gold. 

For the sake of greater solidity, only articles of silver and copper 
and its alloys should be directly gilded, while all other metals are 
best first brassed or coppered. Cleaning from grease and pickling 
is done in the same manner, as described on page 131. The pre- 
paration of the articles for gilding differs from that for silvering 
only in that the surfaces which later on are to appear with high 
lustre are not artificially roughened with emery, pumice, or by 
pickling, because, on the one hand, the gold deposit seldom needs 
to be made extravagantly heavy, and the rough surface formed 
would require more laborious polishing with the burnishers; and, 
on the other, the gold deposits adhere quite well to highly-polished 
surfaces provided the current-strength is correctly regulated, and 
the bath accurately composed according to one of the formulae 
given. Quicking the articles before gilding, which is recom- 
mended by some authors, is not necessary. 

The current-strength must, under no circumstances, be so great 
that a decomposition of water and consequent evolution of hydro- 
gen on the objects take place, since otherwise the gold would not 
deposit in a reguline and coherent form, but as a brown powder. 
By regulating the current-strength so that it just suffices for the 
decomposition of the bath, and avoiding a considerable surplus, a 
very dense and uniform deposit is formed ; and by allowing the 



DEPOSITION OF GOLD. 255 

object to remain long enough in the bath, a beautiful, dull gold 
deposit can be obtained in all the baths prepared according to the 
formulae given. It may, however, be mentioned that this mode 
of dull gilding is the most expensive, since it requires a very 
heavy deposit, and it will, therefore, be better to deaden the sur- 
face previous to gilding according to a process to be described 
later on. 

For gilding with cold baths two freshly filled Bunsen elements 
coupled for tension suffice in almost all cases, while for hot baths 
one element is, as a rule, sufficient, if the anode surface is not too 
small. The more electro-positive the metal to be gilded is, the 
weaker the current can and must be. 

Though gold solutions are good conductors and, therefore, the 
portions which do not hang directly opposite the anodes gild well, 
for the solid gilding of larger objects it is recommended to fre- 
quently change their positions except when they are entirely sur- 
rounded by anodes. 

The inner surfaces of hollow-ware, such as drinking-cups, milk 
pitchers, etc., are best gilded after freeing them from grease and 
pickling, by filling the vessel with the gold bath and suspending 
a current-carrying gold anode in the centre of the vessel, while 
the outer surface of the latter is brought in contact with the 
negative conducting wire. The lips of vessels are gilded by 
placing upon them a cloth rag saturated with the gold bath and 
covering the rag with the gold anode. 

For gilding in the cold bath the process is as follows : The 
objects, thoroughly freed from grease and pickled (and if of iron, 
zinc, tin, Britannia, etc, previously coppered), are hung in the 
bath by copper wires, where they remain with a weak current 
until in about 8 or 10 minutes they appear uniformly gilded. 
At this stage they are taken from the bath, rinsed in a pot filled 
with water, which, after working for some time, is added to the 
bath to replace the water lost by evaporation, and brushed with 
a fine brass scratch-brush and tartar solution. They are then 
thoroughly rinsed, again freed from grease by brushing with lime- 
paste and then returned to the bath, where they remain until they 
have acquired a deposit of sufficient thickness. 

If it is intended to give them a very heavy deposit, it is advis- 



256 ELECTRO-DEPOSITION OF METALS. 

able to scratch-brush them several times with the use of tartar or 
its solution. For gilding by weight the same plan as given for 
silvering (p. 223) is pursued. 

For gilding with the hot bath the operations are the same, with 
the exception that a weaker current is introduced into the bath 
and the time of the gilding process shortened. Frequent scratch- 
brushing also increases the solidity of the deposit and prevents 
the premature turning to a dead brown-black. Since in hot 
gilding more gold than intended is readily deposited, it is espe- 
cially advisable to place a resistance board in the circuit, as other- 
wise the operator must remain standing on the bath and regulate 
the effect of the current by immersing the anodes more or less. 

With a somewhat considerable excess of potassium cyanide, and 
if the objects to be gilded are not rapidly brought in contact with 
the current carrying object rod, hot gold baths cause the solution 
of some metal. Therefore, when silver or silvered objects are 
constantly gilded in them they yield a somewhat greenish gilding 
in consequence of the absorption of silver, or a reddish gilding 
due to the absorption of copper, if copper or coppered articles are 
constantly gilded in them. Hence, for the production of such 
green or reddish color, gilding baths which have thus become 
argentiferous or cupriferous may be advantageously used. In 
order to obtain a deposit of green or red gold with fresh baths, 
the tone-giving addition of metal must be artificially effected, as 
will immediately be seen. 

If, however, such extreme tones are not desired, the content of 
gold in the baths may be exhausted for preliminary gilding with 
the use of platinum anodes, the sad gold color being then given 
in a freshly prepared bath. 

The gold deposits are polished, in the same manner as silver 
deposits, with the burnisher and red ochre, and moistening with 
solution of soap, decoction of flaxseed, or soap-root, etc. 

Red gilding. — In order to obtain a red gold with the formula? 
given, a certain addition of cyanide of copper dissolved in potas- 
sium cyanide has to be made to them. The quantity of such 
addition cannot be well expressed by figures, since the current- 
strength with which the articles are gilded exerts considerable 
influence. It is best to triturate the cyanide of copper in a 



DEPOSITION OF GOLD. 257 

mortar to a paste with water, and add of this paste to a mode- 
rately concentrated potassium cyanide solution as long as cyanide 
of copper is dissolved. Of this copper solution add, gradually 
and in not too large portions, to the gold solution until, with the 
current-strength used, the gold deposit shows the desired red tone. 
The absorption of copper by the bath may also be effected by 
replacing the gold anodes by copper anodes and circulating the 
current (suspending a few gold anodes to the object rod). The 
direct addition of cyanide of copper is, however, preferable. 

For the determination of the content of copper required for 
the purpose of obtaining a beautiful red gold, a bath for hot 
gilding which contained 10.8 grains of gold per quart was com- 
pounded with a solution of cyanide of copper in potassium cyanide 
with 1.08 grains content of copper. The tone of the gilding, 
which previously was pure yellow, immediately passed into a pale 
red gold. By the further addition of 1.08 grains of copper a 
fiery red gold tone was obtained, while a third addition of 1.08 
grains of copper yielded a color more approaching that of copper 
than of gold. These experiments show that 20 per cent, of cop- 
per of the weight of gold contained in the bath seems to be the 
most suitable proportion for obtaining a beautiful red gold. 

Green gilding. — To obtain a greenish gilding, solution of 
cyanide or chloride of silver in potassium cyanide has to be 
added to the gold bath. It is not easy to prepare greenish gild- 
ing of a pleasing color, and to obtain it the current-strength must 
be accurately proportioned to the object-surface, since with too 
weak a current silver predominates in the deposit, the gilding 
then turning out whitish, while too strong a current deposits too 
much gold in proportion to silver, the gilding becoming yellow, 
but not green. 

Rose-color gilding may be obtained by the addition of suitable 
quantities of copper and silver solution, but such coloration, like 
those previously mentioned, requires much attention and reflec- 
tion. Hot gold baths are most suitable for such colorations. 

Dead gilding. — As previously mentioned, a beautiful dead 

gold-deposit may be obtained by the use of any of the formulae 

given and a correctly regulated current, and allowing sufficient 

length of time for gilding ; but the heavy deposit of gold required 

17 



258 ELECTRO-DEPOSITION OF METALS. 

for this process makes it too expensive, and it is therefore ad- 
visable to produce dead gilding without excessively heavy de- 
posits by previous deadening of the basis-surface. The process 
of graining has already been described on p. 237 ; another method 
is to deaden the first thin deposit of gold with the deadening 
scratch-brush, and then to give a second deposit of gold, which 
also turns out dead upon the deadened surface. However, this 
operation of deadening with the scratch-brush requires consider- 
able skill, and it is therefore best to deaden the surface according 
to one of the following methods : — 

For this purpose, the mixture of 1 volume of saturated solution 
of bichromate of potash, and 2 volumes of concentrated hydro- 
chloric acid, mentioned on p. 131, may be used. Brass articles 
are allowed to remain in the mixture several hours, and are then 
quickly drawn through the bright-dipping bath ; 

Or, by depositing upon the articles a coating of frosted silver 
and then gilding in a good gold bath. Unfortunately, this method 
is somewhat expensive, and the burnished parts are greenish. 
Moreover, the intermediary coat of silver is easily affected by 
sulphurous gases, the gilding being thereby blackened. 

More advantageous is the process of providing the articles with 
a dead copper coating in the acid galvanoplastic copper bath, 
then quicking them, and finally gilding. This gilding is very 
handsome in lustre and color. 

Dead gilding on zinc- — By the following process of depositing 
gold on zinc, effects similar to those of fire-gilding on bronze are 
produced. The zinc is first heavily coppered in one of the copper 
baths previously given, and is then brought into a silvering bath 
(with use of a battery) or into an acid copper bath (see " Galvano- 
plasty"), according to whether deadening is to be effected with 
silver or copper. In deadening in the acid copper bath care 
should be taken that the suspending wires are in contact with 
the object-rod before immersing the coppered zinc object in the 
bath. However, this process of coppering zinc in the acid copper 
bath is a very delicate operation, it being frequently observed 
that even with an apparently very heavy coppering in the electro- 
coppering bath, brownish-black spots appear on the objects when 
brought into the acid bath, the copper being deposited on these 



DEPOSITION OF GOLD. 259 

spots in a pulverulent form by the contact of the acid bath with 
the zinc. If this is observed, the objects have to be immediately 
taken from the bath, and after thorough scratch-brushing again 
thoroughly and quickly coppered in the electro-coppering bath 
before returning them to the acid copper bath. It may be re- 
commended, first to provide the coppered zinc objects with a 
thin coat of nickel, and then to copper them in the acid copper 
bath. 

When the deposit seems of sufficient thickness, the zinc is 
washed in a large quantity of water, drawn through a weak 
solution of mercurous nitrate, and brought into a hot gilding 
bath composed as follows: Water 10 quarts, sodium phosphate 
21 ozs., sodium bisulphite 3§- ozs., potassium cyanide 11 \ 
drachms, gold (in the form of chloride) of drachms. 

At first quite a strong current is used, which is gradually re- 
duced up to the moment when the object is taken from the bath. 

Coloring of the gilding. — It has been frequently mentioned that 
the most rational and simple process of giving certain tones of 
color to the gilding is by means of a stronger or weaker current. 
Many operators, however, cling to the old method of effecting the 
coloration by gilder's wax or brushing with certain mixtures, and 
for this reason this process, which is generally used for coloring 
fire-gilding, shall be briefly mentioned. 

To impart to the gold-deposit a redder color, the gilding-wax 
is prepared with a greater content of copper, while for greenish 
gilding more zinc-salt is added. There are innumerable receipts 
for the preparation of gilding- wax, nearly every gilder having 
his own receipt, which he considers superior to all others. Only 
two formulae which yield good results will here be given, one (I.) 
for reddish gilding and one (II.) for greenish gilding. 

I. Wax 12 parts by weight, pulverized verdigris 8, pulverized 
sulphate of zinc 4, copper scales 4, borax 1, pulverized blood- 
stone 6, copperas 2. 

II. Wax 12 parts by weight, pulverized verdigris 4, pulverized 
sulphate of zinc 8, copper scales 2, borax 1, pulverized bloodstone 
6, copperas 2. 

Gilder's wax is prepared as follows : Melt the wax in an iron 
kettle, add to the melted mass, with constant stirring, the other 



260 ELECTEO-DEPOSITION OF METALS. 

ingredients, pulverized and intimately mixed, in small portions, 
and stir until cold, so that the powder cannot settle on the 
bottom or form lumps. Finally mould the soft mass into sticks 
about ^ inch in diameter. 

The operation for applying the gilder's wax is as follows : Coat 
the heated gilded articles uniformly with the wax and burn oif 
over a charcoal fire, frequently turning the articles. After the 
extinguishment of the wax flames plunge the articles into water, 
scratch-brush with wine-vinegar, dry in sawdust, and polish. 

To give gilded articles a beautiful, rich appearance, the follow- 
ing process may also be used : Mix 3 parts by weight of pulverr 
ized alum, 6 of saltpetre, 3 of sulphate of zinc, and 3 of common 
salt, with sufficient water to form a thinly-fluid paste. Apply 
this paste as uniformly as possible to the articles by means of a 
brush, and after drying, heat the coating upon an iron plate until 
it turns black ; then wash in water, scratch-brush with wine- 
vinegar, dry, and polish. 

According to a French receipt, the same result is attained by 
mixing pulverized blue vitriol 3 parts by weight, verdigris 7, 
sal ammoniac 6, and saltpetre 6, with acetic acid 31 ; immersing 
the gilded articles in the mixture or applying the latter with a 
brush ; then heating the objects upon a hot iron plate until they 
turn black, and, after cooling, pickling in concentrated sulphuric 
acid. 

Some gilders improve bad tones of gilding by immersing the 
articles in dilute solution of nitrate of mercury until the gilding 
appears white ; the mercury is then evaporated over a flame and 
the articles are scratch-brushed. Others apply a paste of pulveiv 
ized borax and water, heat until the borax melts, and then quickly 
immerse in dilute sulphuric acid. 

Incrustations with gold are produced in the same manner as in- 
crustations with silver described on p. 240. •; 

Gilding of metallic wire and gauze. — Fine wire of gilded cop per 
and brass is much used in the manufacture of metallic fringes and 
lace, for epaulettes and other purposes. The fine copper and brass 
wires being drawn through the draw-irons and wound upon spools 
by special machines, and hence not touched by the hands, freeing 
from grease may, as a rule, be omitted. The first requisite for 



DEPOSITION OF GOLD. 



261 



gilding is a good winding machine, which draws the wires through 
the gold bath and wash boxes, and further effects the winding of 
the wire upon spools. The principal demand made in the con- 
struction of such a machine is that by means of a simple manipu- 
lation a great variation in the speed with which the wire or gauze 
passes through the gold bath can be obtained. This is necessary 
in order to be able to regulate the thickness of the gilding by the 
quicker or slower passage of the wire. A machine well adapted 
for this purpose is that constructed by J. W. Spaeth and shown 
in Fig. 115. 

Fig. 115. 










"laAlUMUni II HI! 

mams ' '"^ I rail 
m " I'-r - ' 




The variation in the passage of the wire is attained by the 
two friction-pulleys F, which sit upon a common shaft with the 
driving-pulley R, and transmit their velocity by means of the 
friction-pistons KK' to the friction-pulley F', which is firmly con- 
nected to the belt-pulley R driving the spool spindle. Since by 
a simple device the pistons iTand K' may be shifted, it is clear that 
the transmission of the number of revolutions from i^to F' is de- 
pendent on the position of the friction pistons _5Tand K r , and that 
the velocity will be the greater the shorter the distance they are 
from the centre of the friction-pulleys F and F' . In order that 
the friction between F, K, and F' may always be sufficient for the 



262 ELECTRO-DEPOSITION OF METALS. 

transmission of the motion, even when the pistons are worn, four 
weights, G, are provided, which press the above-mentioned parts 
firmly against each other. 

In front of each spool of this machine is inserted a small 
enamelled iron vat which contains the gold bath, and is heated by 
a gas flame to about 167° F. Between this bath and the winding 
machine is another small vat with hot water in which the gilded 
wire is rinsed. 

The wires unwind from a reel placed in front of the gold baths, 
run over a brass drum which is connected to the negative pole of 

Fig. 116. 



the source of current, and transmits the current to the wires ; the 
dipping of the wires into the gold bath is effected by porcelain 
drums, which are secured to heavy pieces of lead placed across the 
vats as shown in Fig. 116. The gilded wire being wound upon 
the spools of the winding machine, these spools are removed and 
thoroughly dried in the drying chamber. The wire is then again 
reeled off on to a simple reel, in doing which it is best to pass it 
through between two soft pieces of leather to increase its lustre. 

The most suitable gold bath is that prepared according to 
formula IV. ; the current-strength should be from 6 to 8 volts, 
which will produce a deposit of sufficient thickness even with the 
wire passing at the most rapid rate through the bath. 

Gilding by contact, by immersion, and by friction. — For contact 
gilding by touching with zinc, formulae I., II., IV., and V., may be 
used, IV. and V. being especially suitable if the addition of potas- 
sium cyanide is somewhat increased and the baths are sufficiently 
heated . 

A contact gold bath prepared with yellow prussiate of potash 
according to the following formula also yields a good deposit: 
VIII. Fine gold as chloride of gold 54 grains, yellow prussiate of 
potash 1 oz., potash 1 oz., common salt 1 oz., water 1 quart. The 



DEPOSITION OF GOLD. 263 

batli is prepared as given for formula III. ; for use, heat it to 
boiling. 

Gilding by contact is done the same way as silvering by con- 
tact. The points of contact must be frequently changed, since in 
the gold bath intense stains are still more readily formed than in 
the silver bath. 

For gilding by contact, Conrad Taucher recommends the fol- 
lowing bath : Distilled water 10 quarts, sodium or potassium 
pyrophosphate 28 ozs., prussic acid \\ drachms, crystallized 
chloride of gold 13| drachms. 

To prepare the bath, bring into a porcelain vessel or into a dish 
of enamelled cast-iron 9 quarts of distilled* water and add the 
28 ozs. of pyrophosphate, stirring constantly with a glass rod. 
Then heat, and when solution is complete filter and set aside to 
cool. 

While filtering the solution the chloride of gold is prepared by 
bringing into a small glass flask 5J drachms of fine rolled gold, 
14 drachms of pure hydrochloric acid, and 8 \ drachms of pure 
nitric acid. Apply a gentle heat to the bottom of the flask. In 
a few seconds vigorous effervescence accompanied by the evolution 
of orange-red vapors takes place, and the gold in a few minutes 
dissolves to a reddish-yellow fluid. To evaporate an excess of 
acids, which if brought into the bath might cause serious disturb- 
ances and even render the bath entirely useless, the flask is placed 
upon a piece of sheet-iron provided in the centre with a hole 
about 0.11 inch in diameter, and heated upon a stove or over a 
spirit lamp. When no more vapors escape and the solution has 
become thickly fluid and has acquired an intense hyacinth-red 
color, remove the flask by means of wooden pincers from the fire 
and let cool. If properly prepared, the chloride of gold then 
congeals to an aggregate of saffron-yellow acicular crystals. If 
the color of the latter is red, too much heat has been applied. 
Such chloride of gold is very suitable for the preparation of 
electro-gilding baths, but if it is to be used for contact gilding a 

* The use of distilled water is necessary, otherwise the lime salts contained 
in ordinary water would decompose a portion of the pyrophosphate. 



264 



ELECTRO-DEPOSITION OF METALS. 



small quantity of the above-mentioned two acids has to be added, 
and, after heating, the mass has to be again evaporated. 

It frequently happens that by careless manipulation the gold 
is " burnt," i. e., the auric chloride is decomposed by too long, 
continued heating and is converted into insoluble aurous chloride, 
or even into pulverulent metallic gold. If such is the case, the 
treatment with the above-mentioned mixture of acids has to be 
repeated. The object of the perforated piece of sheet-iron on 
which the flask is placed for the purpose of evaporating the 
solution is to prevent the sides of the flask from being heated 
too strongly, as otherwise the thin layers of chloride of gold 
solution might be decomposed. 

In practice porcelain capsules which are heated in a sand bath 
are generally used for dissolving gold. Fig. 117 shows such a 
capsule with glass funnel in a sand bath over a gas stove. The 
purpose of the glass funnel is to prevent any fluid from being 
thrown from the capsule at the moment of effervescence caused 
by the action of the acids upon the metal. 

Fig. 117. 




The cold crystallized chloride of gold in the flask or the cap- 
sule is now dissolved in a small quantity of distilled water, solution 
being effected almost immediately. The solution is poured upon 
a filter of filtering paper in a glass funnel placed upon a clean 
bottle. A small piece of paper should be inserted between the 



DEPOSITION OF GOLD. 2G5 

funnel and the neck of the bottle, so that the air can escape from 
the latter and the fluid run oif from the filter. 

The object of filtering is to separate the small quantity of 
chloride of silver formed from the little silver which is present 
even in the purest commercial gold. To bring all the gold into 
the bath repeatedly wash the bottle and the filter with a small 
quantity of distilled water. 

Now mix the cold solution of the pyrophosphate and that of 
the chloride of gold by pouring the latter gradually into the 
former and stirring with a glass rod. Then add the 4| drachms 
of prussic acid and heat to the boiling-point, when the bath is 
ready for use. 

When mixed cold the bath has a yellow or yellow-greenish 
color, which disappears as the temperature rises. However, the 
fluid sometimes becomes currant-red or violet, which indicates that 
it contains too little prussic acid. This is remedied by adding 
drop by drop prussic acid until the fluid is entirely discolored. 
Great care must, however, be exercised in adding the acid, as an 
excess of it renders the gilding pale. 

By following the directions above given, the bath is very suit- 
able for producing a beautiful yellow gilding on objects previously 
thoroughly cleansed. The articles should be passed through a 
very weak solution of mercurous nitrate, otherwise the gilding 
shades and becomes reddish. The articles to be gilded must be 
constantly moved in the bath ; they are suspended to hooks or 
brought into the bath in dipping baskets of stoneware or brass. 

Gilding is finished in a few seconds. The articles are then 
washed in clean water, dried in dry and warm sawdust, and, if 
necessary, immediately polished. 

By neglecting the precautionary measures given above, the gild- 
ing sometimes appears tarnished and dissimilar in tone.. It is 
then colored or treated with the so-called matt for gilded articles. 

For this purpose melt equal parts of the following salts in their 
water of crystallization at about 212° F. : Ferrous sulphate (green 
vitriol), zinc sulphate (white vitriol), alum, and saltpetre. 

Thoroughly wet every portion of the defective gilding by turn- 
ing the articles about in this mixture. Then place them in the 
centre of a cylindrical stove, in which the coal burns between the 



266 ELECTRO-DEPOSITION OF METALS. 

sides and a cylindrical grate, so that the entire heat radiates to- 
ward the empty space in the centre. The salts melt and then get 
into a fiery flux, the entire mass acquiring a dull earthen color. 
When on touching the articles with the moistened finger a slight 
hissing noise is heard, the temperature is sufficiently high and the 
articles are thrown into weak starch water acidulated with sul- 
phuric acid. The coating of salts dissolves immediately and the 
gilding presents a beautiful warm and uniform appearance. This 
operation can, of course, only be executed if the entire article has 
been gilded. 

For baths for gilding by dipping the following two formulas have 
stood the test: I. Crystallized sodium pyrophosphate 2.82 ozs., 
12 per cent, prussic acid 4.51 drachms, crystallized chloride of 
gold 1.12 drachms, water 1 quart. Heat the bath to the boil- 
ing-point, and immerse the pickled objects of copper or its alloys, 
moving them constantly until gilded. Iron, steel, tin, and zinc 
should previously be coppered ; coating the objects with mercury 
(quicking) before immersion being entirely superfluous. 

All gold baths prepared with sodium pyrophosphate give rapid 
and beautiful results when fresh, but they have the disadvantage 
of quickly decomposing, and consequently can seldom be com- 
pletely exhausted. In this respect the following formula answers 
much better: — 

II. Crystallized sodium phosphate 2.82 drachms, chemically 
pure caustic potash 1.69 drachms, chloride of gold 0.56 drachm, 
98 per cent, potassium cyanide 9.03 drachms, water 1 quart. Dis- 
solve the sodium phosphate and caustic potash in f- of the water, 
and the potassium cyanide and chloride of gold in the remaining \. 
Heat the solution to the boiling-point. The bath can be almost 
entirely exhausted, it not being decomposed by keeping. Should 
the bath become weak, add about 2.82 drachms of potassium 
cyanide, and use it for preliminary dipping until no more gold is 
reduced. To complete the coating, the objects subjected to such 
preliminary dipping are then immersed for a few seconds in a 
freshly prepared bath of the composition given above. 

The layer of gold formed is in all cases very thin, the amount 
of gold deposited corresponding to the quantity of basis- metal 
which has been dissolved. 



DEPOSITION OF GOLD. 267 

III. One of the best directions for gilding without the use of 
a current is, according to the " Edelmetallindustrie," as follows : 
Prepare a solution of gold in aqua regia (2 parts hydrochloric 
acid and 1 part nitric acid). The solution of the gold is effected 
in a porcelain dish, best in a sand or water bath, whereby heavy 
brown acid vapors of hyponitrous acid are evolved. When all is 
dissolved allow the acid to evaporate until the fluid has acquired 
a deep brown color and no more acid vapors arise. Then, after 
cooling, dilute the solution with water and keep it in a bottle for 
future use. Next dissolve in the bath 6f drachms of potassa and 
11^ drachms of sodium phosphate, and add enough gold solution 
that the bath contains about 2\ drachms of gold. To this bath, 
containing about 8 to 10 quarts of fluid, add carefully, with 
constant stirring, If ozs. of potassium cyanide, and then let it 
thoroughly boil for some time. After cooling the bath to about 
176° or 158° F., suspend the articles in it and keep the bath at 
this temperature. The bath only requires an occasional addition 
of gold solution (when the gilding becomes gray or dirty), or of 
potassium cyanide (when the gilding becomes foxy), and, with 
proper treatment, can be used for a long time. 

Gilding of porcelain, glass, etc. — The pyrophosphate baths 
given above may be advantageously employed for gilding porce- 
lain, glass, stoneware, etc. the process being as follows : — 

Neutral platinic chloride is intimately triturated with enough 
lavender oil to form a thin syrup. Of this preparation a scarcely 
perceptible film is applied by means of a small brush to the 
article to be ornamented. When dry, the article is heated in a 
muffle to a dark red heat. At this temperature the essential oil 
partially volatilizes, while another portion is decomposed, and 
reduces by its hydrogen the platinic chloride to metallic platinum, 
the result being a coating of metal of a finely polished appearance. 
When cold the article is immediately drawn through nitric acid, 
which does not attack the platinum, but removes any impurities 
which might make its surface dull. The article is then washed 
in a large quantity of water, wrapped with fine brass wire in such 
a manner that the wire touches the platinized places at many 
points, and is then brought into the gold bath. In a few minutes 



268 ELECTRO-DEPOSITION OF METALS. 

the platinum is coated with a beautiful smooth film of gold, 
which adheres well, and only requires rubbing with chamois. 

By this method the expensive work of polishing is rendered 
unnecessary, which with articles having many depressed places 
is besides almost impossible. If the gilding is too red, add to the 
bath a few drops of the double cyanide of potassium and silver. 

Gilding by friction. — This process is variously termed gilding 
with the rag, with the thumb, with the corh. It is chiefly employed 
upon silver, though sometimes also upon brass and copper. The 
operation is as follows: Dissolve 1.12 to 1.69 drachms of chloride 
of gold in as little water as possible, to which has previously been 
added 0.56 drachm of saltpetre. Dip in this solution small linen 
rags, and, after allowing them to drain off, dry them in a da^k 
place. These rags saturated with gold solution are then charred 
to tinder at not too great a heat, whereby the chloride of gold is 
reduced, partially to protochloride and partially to finely divided 
metallic gold. This tinder is then rubbed in a porcelain mortar 
to a fine uniform powder. 

To gild with this powder, dip into it a charred cork moistened 
with vinegar or salt water and rub, with not too gentle a pressure, 
the surface of the article to be gilded, which must be previously 
cleansed from adhering grease. The thumb of the hand may be 
used in place of the cork, but in both cases care must be had not 
to moisten it too much, as otherwise the powder takes badly. 
After gildiug the surface may be carefully burnished. 
. For gilding by friction a solution of chloride of gold in an 
excess of potassium cyanide may also be used, after thickening 
the solution to a paste by rubbing in whiting. The paste is ap- 
plied to the previously zincked metals by means of a cork, piece 
of leather, or a brush. Martin and Peyraud, the originators of 
this method, describe the operation as follows : Articles of other 
metals than zinc are placed in a bath consisting of concentrated 
solution of sal ammoniac, in which has been placed a quantity of 
granulated zinc. The articles are allowed to boil a few minutes, 
whereby they acquire a coating of zinc. For the preparation of 
the gilding composition, dissolve 11.28 drachms of chloride of gold 
in a like quantity of water, and add a solution of 2.11 ozs. of 
potassium cyanide in as little water as possible (about 2.8 ozs.). 



DEPOSITION OF GOLD. 269 

Of this solution add so much to a mixture of 3.52 ozs. of fine 
whiting and 2.82 drachms of pulverized tartar that a paste is 
formed which can be readily applied with a brush to the article 
to be gilded. When the article is coated, heat it to between 140° 
and 158° F. After removing the dry paste by washing the 
gilding appears and can be polished with the burnisher. 

Fire or mercury gilding.- — Before the introduction of electro- 
plating, nearly all substantial gilding was effected by this process. 
However, the cost is much greater, the execution of the process 
presenting many difficulties, and besides the workman is con- 
stantly exposed to the very injurious mercurial vapors. The 
resulting gilding, however, is distinguished by great solidity. 

The execution of fire gilding begins with the preparation of the 
amalgam of gold. For this purpose put a weighed quantity of 
fine gold in a crucible and heat to dull redness. The requisite 
proportion of mercury, 8 parts to 1 of gold, is now added, and 
the mixture is stirred with a slightly crooked iron rod, the heat 
being kept up until the gold is entirely dissolved by the mer- 
cury. Pour the amalgam into a small dish about 3 parts filled, 
with water and work about with the fingers under the water to 
squeeze out as much of the excess of mercury as possible. To 
facilitate this the dish is slightly inclined to allow the superfluous 
mercury to flow from the mass, which soon acquires a pasty condi- 
tion capable of receiving the impression of the fingers. Afterward 
squeeze the amalgam in a chamois leather bag, by which a further 
quantity of mercury is liberated. The amalgam, which remains 
after this final treatment, consists of about 33 parts of mercury 
and 57 parts of gold in 100 parts. The mercury which is pressed 
through the bag retains a good deal of gold, and is employed in 
preparing fresh batches of amalgam. It is important that the 
mercury employed should be pure. 

To apply the amalgam, a solution of nitrate of mercury is em- 
ployed, which is prepared by dissolving in a glass flask 100 parts 
of mercury in 110 parts of nitric acid of specific gravity 1.33, 
gentle heat being employed to assist the chemical action. The 
red fumes given off must be allowed to escape into the chimney, 
since they are very deleterious when inhaled. When the mercury 



270 ELECTRO-DEPOSITION OF METALS. 

is all dissolved the solution is to be diluted with about 25 times 
its weight of distilled water and bottled for use. 

The pasty amalgam is spread with the blade of a knife upon a 
hard, flat stone. The article, after being well cleaned and scratch- 
brushed, is treated as follows : Take a small scratch- brush, 
formed of stout brass wire, dip in the solution of nitrate of mer- 
cury, then draw over the amalgam ; pass the brush carefully over 
the surface to be gilded, repeatedly dipping the brush in the mer- 
curial solution and drawing it over the amalgam until the entire 
surface is uniformly and sufficiently coated. Then rinse the 
article well, and dry. The next operation is the evaporation of 
the mercury. For this purpose a charcoal fire, resting upon a 
cast-iron plate, has been generally adopted, a simple hood of 
sheet-iron being the only means of protection from the injurious 
effects of the mercurial vapors. "When the amalgamated article 
is rinsed and dried, it is exposed to the glowing charcoal, turned 
about and heated by degrees to the proper point, then it is with- 
drawn from the fire by means of long pincers or tongs. The 
article is then taken in the left hand, which should be protected 
with a leather glove, turned over the fire in every direction, and 
while the mercury is volatilizing the article should be struck with 
a long-haired brush to equalize the amalgam coating and force it 
upon such parts as may appear to require it. When the mercury 
has become entirely volatilized the gilding has a dull, greenish- 
yellow color. If any bare places are apparent, they are touched 
up with amalgam and the article is again submitted to the fire, 
care being taken to expel the mercury gradually. The article is 
then well scratch-brushed ; when it is of a pale greenish color 
heat it again to expel any remaining mercury, when it acquires 
the orange-yellow of fine gold. If required to be bright, it is 
burnished in the ordinary way. If the gilding is to be dead, 
secure the article by means of iron wire to the end of an iron rod 
and coat it with a hot paste consisting of saltpetre, common salt, 
and alum ; then expose the article to a bright fire, turning it in 
every direction until the coat of the mixture fuses and begins to 
run off; then remove the article from the fire and throw it in a 
wooden vat containing a large quantity of water. The coat of 
salts covering the article is immediately dissolved, and the gilding 



DEPOSITION OF GOLD. 271 

presents a beautiful dead appearance. To stand this process of 
deadening the article must be well gilded, especially, as frequently 
happens, if the operation does not succeed the first time. 

Red streaks are frequently observed on otherwise successful 
gilding. These streaks are caused by the iron wire which has 
been wrapped round the article. They disappear by plunging 
the article in dilute nitric acid, or, still better, in pure hydro- 
chloric acid. 

For the sake of completeness, a method of gilding which gives 
to some parts of the article a lustrous and to others a dead ap- 
pearance may here be mentioned. It is a combination of fire- 
gilding with electro-deposition, the dead places being produced 
by the former operation and the lustrous places by the latter. 
The operation is as follows : The places which are to be dead are 
first gilded with amalgam, heated, scratch-brushed, and raised. 
The entire article is then gilded with the assistance of the battery, 
no attention being paid to any gold depositing upon the surfaces 
already gilded. The entire surface is then carefully scratch- 
brushed, and the electro-gilded surfaces are next coated with a 
paste of flake-white, water, and glue, and then with a thick paste 
of clay, the fire-gilded surfaces remaining free. The whole is 
then allowed to dry, when the fire-gilded surfaces are deadened 
by being treated, as above described, with a hot paste of saltpetre, 
common salt, and alum, the coatings of flake-white and clay are 
then dissolved by means of water acidulated with hydrochloric 
acid. The only purpose of these coatings is to prevent a too in- 
tense action of the heat upon the electro-gilded portions. The 
latter, if necessary, are then again scratch-brushed, which must, 
however, be done with the greatest care, to avoid injury to the 
dead portions. The article is finally polished. 

The method above described is generally used, but it has many 
disagreeable features, amongst others, that the places which are 
exposed to too strong a heat, or which have not been sufficiently 
gilded, frequently show red stains. 

The following process is better and more convenient : — 

The surfaces, which are to remain dead, are first gilded and 
deadened, and then coated with varnish. When dry the article 
is pickled ; the acid does not attack the varnished surfaces. The 



272 ELECTRO-DEPOSITION OF METALS. 

object is then brought into the electro-gilding bath, which also 
does not attack the varnish. When the desired shade of gold has 
been obtained, the article is taken from the bath and the varnish 
removed by means of benzine. The article is then washed in a 
warm potassium cyanide solution, next in boiling water, and 
finally dried. The dead gilding, no matter by which process it 
may have been produced, is only suitable for articles not exposed 
to friction, a slight touch with the fingers being sufficient to de- 
prive it of its delicate lustre. 

Old dead gilding may be improved by boiling with potash 
and washing in dilute sulphuric or nitric acid. This suffices for 
the removal of stains caused by grease, smoke, or dust. If, how- 
ever, the gilding is worn off, the article has to be scratch-brushed 
and regilt. 

Du Fresne gives a method of gilding, which is also a combi- 
nation of fire-gilding with electro-deposition. It is executed as 
follows : — 

The articles are galvanized with the assistance of the current, 
in a mercurial solution consisting of cyanide of mercury in potas- 
sium cyanide with additions of carbonate and phosphate of soda, 
then gilded in an ordinary gilding bath, next again coated with 
mercury, then again gilded, and so on, until a deposit of suffi- 
cient thickness is obtained. The mercury is then evaporated 
over glowing coals, and the articles, after scratch-brushing, are 
burnished. 

According to another process, the articles are gilded in a bath 
consisting of 98 per cent, potassium cyanide 1.2 ozs., cyanide of 
gold 92| grains, cyanide of mercury 92J grains, distilled water 
1 quart, a strong current being used. The articles being suffi- 
ciently gilded, the mercury is evaporated, the articles scratch- 
brushed and finally polished. 

Removing gold from gilded articles — "Stripping." — Gilded 
articles of iron and steel are best stripped by treating them as the 
anode in a solution of from 2 to 2f ozs. of 98 per cent, potas- 
sium cyanide in 1 quart of water, and suspending a copper plate 
greased with oil or tallow as the cathode. Gilded silverware is 
readily stripped by heating to glowing and then immersing in 
dilute sulphuric acid, whereby the layer of gold cracks off', the 



DEPOSITION OF GOLD. 273 

glowing and immersing in dilute sulphuric acid being repeated 
until all the gold is removed. Before glowing and immersing in 
dilute sulphuric acid, the articles may first be provided with a 
coating of a paste of sal ammoniac, flowers of sulphur, borax, 
and nitrate of potash, which is allowed to dry. On the bottom 
of the vessel containing the dilute sulphuric acid the gold will be 
found in lamina? and scales, which are boiled with pure sulphuric 
acid, washed, and finally dissolved in aqua regia, and made into 
chloride of gold or fulminating gold. 

To strip articles of silver, copper, or German silver which will 
not bear glowing, the solution of gold may be effected in a mix- 
ture of 1 lb. of fuming sulphuric acid, 2.64 ozs. of concentrated 
hydrochloric acid, and 1.3 ozs. of nitric acid of 40° Be. Dip 
the articles in the warm acid mixture and observe the progressive 
action of the mixture by frequently removing the articles from 
it. The articles to be treated must be perfectly dry before 
immersing in the acid mixture, and care must be had to preserve 
the latter from dilution with water in order to prevent the acids 
from acting upon the basis-metal. 

Determination of genuine gilding. — Objects apparently gilded 
are rubbed upon the touchstone and the streak obtained is treated 
with pure nitric acid of 1.30 to 1.35 specific gravity. The metal 
contained in the streak thereby dissolves, and as far as it is not 
gold disappears, while the gold remains behind. The stone 
should be thoroughly cleansed before each operation, and the 
streak should be made not with an edge or a corner of the object 
to be tested, but with a broader surface. If no gold renjains 
upon the stone, but there is, nevertheless, a suspicion of the 
article being slightly gilded, proceed with small articles as fol- 
lows : Take hold of the article with a pair of tweezers, and 
after washing it first with alcohol, and then with ether, and 
drying upon blotting paper, pour over it in a test glass, cleansed 
with alcohol or ether, according to the weight of the article, 0.084 
to 5.64 drachms of nitric acid of 1.30 specific gravity free from 
chlorine. The article will be immediately dissolved, and if it has 
been gilded never so slightly, perceptible gold spangles will remain 
upon the bottom of the glass. 
18 



274 ELECTRO-DEPOSITION OF METALS. 

Recovery of gold from gold baths, etc. — To recover the gold 
from old cyanide gilding baths, evaporate the bath to dryness, 
mix the residue with litharge, and fuse the mixture. The gold is 
contained in the lead button thus obtained. The latter is then 
dissolved in nitric acid, whereby the gold remains behind in the 
form of spangles. These spangles are filtered off and dissolved 
in aqua regia. 

The following method is used for the recovery of gold by the 
wet process: The bath containing gold, silver, and copper is 
acidulated with hydrochloric acid, which causes a disengagement 
of hydrocyanic acid. This gas is extremely poisonous, for which 
reason the operation should be carried on in the open air or where 
there is a good draught or ventilation to carry off the fumes. 
A precipitate consisting of the cyanides of gold and copper and 
chloride of silver is formed. This is well washed and boiled in 
aqua regia, which dissolves the gold and copper as chlorides, 
leaving the chloride of silver behind. The solution containing 
the gold and copper is evaporated nearly to dryness in order to 
remove the excess of acid, the residue is dissolved in a small 
quantity of water, and the gold precipitated therefrom as a brown 
metallic powder by the addition of sulphate of iron (copperas). 
The copper remains in solution. 

Finely divided zinc — so-called zinc-dust — is an excellent agent 
for the precipitation of gold in a pulverulent form from cyanide 
gilding baths. By adding zinc-dust to an exhausted cyanide 
gilding bath, and thoroughly shaking or stirring it from time 
to time, all the gold is precipitated in two or three days. The 
quantity of zinc required for precipitation depends of course on 
the quantity of gold present, but, generally speaking, J or at the 
utmost 1 lb. of zinc-dust will be required for 100 quarts of ex- 
hausted gilding bath. 

The pulverulent gold obtained is washed, treated first with 
hydrochloric acid to remove adhering zinc-dust, and next with 
nitric acid to free it from silver and copper. 

From the acid mixtures serving for dead pickling gold, or for 
stripping, the gold is precipitated by solution of sulphate of iron 
(copperas) added in excess. The gold present is precipitated as a 
brown powder mixed with ferric oxide. This powder is filtered 



DEPOSITION OF PLATINUM AND PALLADIUM. 275 

off and treated in a porcelain dish with hot hydrochloric acid, 
which dissolves the iron. The gold which remains behind is 
then filtered off, and, after washing, dissolved in aqua regia in 
order to work the solution into fulminating gold or neutral 
chloride of gold. 



CHAPTER XI. 

DEPOSITION OF PLATINUM AND PALLADIUM. 

1 . Deposition of Platinum. 

Properties of platinum. — Pure platinum is white with a grayish 
tinge ; it is as soft as copper, malleable, and very ductile. At a 
white heat it can be welded, but is fusible only with the oxy hy- 
drogen blowpipe or by the electric current. Its specific gravity 
is 21.4. 

Air has no oxidizing action upon platinum ; it is scarcely acted 
upon by any single acid; prolonged boiling with concentrated 
sulphuric acid appears to dissolve the metal slowly. The best 
solvent for it is aqua regia, which forms the tetrachloride, PtCl 4 . 
Chlorine, bromine, sulphur, and phosphorus combine directly with 
platinum, and fusing saltpetre and caustic alkali attack it. 

Besides in the malleable and fused state, platinum may be ob- 
tained as a very finely divided powder, the so-called platinum 
black, which is precipitated with zinc from dilute solution of pla- 
tinum chloride acidulated with hydrochloric acid. 

Platinum baths. — The platinum baths formerly proposed did 
not yield quite satisfactory results, the content of platinum being 
too small in some of them, while with others dense deposits could 
not be obtained. A new formula by Bottger gives, however, 
quite a good bath : A moderately dilute solution of sodium citrate 
is added to platoso-ammonium chloride, until an excess of the 
latter no longer dissolves, even after continued boiling. The 
following proportions have been found very suitable : Dissolve 
17J ozs. of citric acid in 2 quarts of water, and neutralize with 
caustic soda. To the boiling solution add, with constant stirring, 



276 ELECTKO-DEPOSITION OF METALS. 

the platoso-ammonium chloride freshly precipitated from 2.64 
ozs. of chloride of platinum, heat until solution is complete, allow 
to cool, and dilute with water to 5 quarts. To decrease the re- 
sistance of the bath, 0.7 or 0.8 oz. of sal ammoniac may be added ; 
a larger addition, however, causing the separation of dark-colored 
platinum. 

The platoso-ammonium chloride is prepared by adding to a 
concentrated solution of chloride of platinum concentrated solution 
of sal ammoniac until a yellow precipitate is no longer formed on 
adding a further drop of sal ammoniac. The precipitate is 
filtered off and brought into the boiling solution of sodium citrate. 
This bath works very uniformly if the content of platinum is 
from time to time replenished. 

" The Bright Platinum Plating Company," of London, has 
recently patented the following composition of a platinum bath : 
Chloride of platinum 0.98 oz., sodium phosphate I9| ozs., ammo- 
nium phosphate 3.95 ozs., sodium chloride 0.98 oz., and borax 
0.35 oz., are dissolved, with the aid of heat, in 6 to 8 quarts of 
water, and the solution is boiled for 10 hours, the water lost by 
evaporation being constantly replaced. The results obtained with 
this bath were not much better than with Bottger's. 

Dr. W. H. Wahl gives the following directions for preparing 
platinum baths :* — 

Alkaline platinate bath. — Platinic hydrate 2 ozs., caustic potassa 
(or soda) 8 ozs., distilled water 1 gallon. 

Dissolve one-half of the caustic potassa in a quart of distilled 
water, add to this the platinic hydrate in small quantity at a time, 
facilitating solution by stirring with a glass rod. When solution 
is effected, stir in the other half of alkali dissolved in a quart of 
water ; then dilute with enough distilled water to form one gallon 
of solution. To hasten solution, the caustic alkali may be gently 
heated, but this is not necessary, as the platinic hydrate dissolves 
very freely. This solution should be worked with a current of 
about two volts, and will yield metal of an almost silvery white- 
ness upon polished surfaces of copper and brass, and quite freely. 
There should be slight, if any, perceptible evolution of hydrogen 

* Journal of the Franklin Institute, July, 1890. 



DEPOSITION OF PLATINUM AND PALLADIUM. 277 

at the cathode, but a liberal evolution of oxygen at the anode. 
An addition of a small proportion of acetic acid to this bath 
improves its operation where a heavy deposit is desired. The 
anode must be of platinum or carbon, and owing to the readiness 
with which the metal is deposited an excess of anode-surface is 
to be avoided. Articles of steel, nickel, tin, zinc, or German sil- 
ver will be coated with black and more or less non-adherent plati- 
num ; but by giving objects of these metals a preliminary thin 
electro-deposit of copper in the hot cyanide bath they may be 
electro-platinized in the alkaline platinate bath equally as well as 
copper. The bath may be worked hot or cold, but it is recom- 
mended to work it at a temperature not exceeding 100° F. It 
may be diluted to one-half the strength indicated in the formula 
and still yield excellent results. The surface of the objects should 
be highly polished by buffing or otherwise prior to their intro- 
duction into the bath, if the resulting deposit is designed to be 
brilliant. 

The deposition of platinum takes place promptly. In five 
minutes a sufficiently heavy coating will be obtained for most 
purposes. The deposited metal is so soft, however, that it requires 
to be buffed very lightly. A heavier deposit will appear gray in 
color, but will accept the characteristic lustre of platinum beneath 
the burnisher. 

An oxalate solution is prepared by dissolving 1 oz. of platinic 
hydrate in 4 ozs. of oxalic acid and diluting the solution to the 
volume of one gallon with distilled water. The solution should 
be kept acidified by the occasional addition of some oxalic acid. 
The simplest plan of using this bath, which requires no atten- 
tion to proportions, is simply to work with a saturated solution 
of the oxalate, keeping an undissolved excess always present at 
the bottom of the vessel . An addition of a small quantity of oxalic 
acid now and then will be found advantageous. The double 
salts of oxalic acid with platinum and the alkalies may be formed 
by saturating the binoxalate of the desired alkali with platinic 
hydrate and maintaining the bath in normal metallic strength by 
the presence of an undissolved residuum of platinous oxalate. 

The double oxalates are not so soluble in water as the simple 
salt. The oxalate baths, both of single and double salts, may be 



278 ELECTRO-DEPOSITION OP METALS. 

worked cold or hot (though not to exceed 150° F.) with a current 
of comparatively low pressure. The metal will deposit bright, 
reguline, and adherent on copper and brass. Other metallic ob- 
jects must receive a preliminary coppering as above. The de- 
posited metal is dense, with a steely appearance, and can be 
obtained of any desired thickness. 

The deposit obtained in the oxalate bath is sensibly harder 
than that from the alkaline platinate bath and will bear buffing 
tolerably well. 

The 'phosphate bath may be prepared by the following formula : 

Phosphoric acid, syrupy (specific gravity 1.7), 8 ozs., platinic 
hydrate 1 to 1J ozs., distilled water 1 gallon. 

The acid should be moderately diluted with distilled water and 
the solution of the hydrate effected at the boiling temperature. 
Water should be added cautiously from time to time to supply 
that lost by evaporation. When solution has taken place, the 
same should be diluted with sufficient water to make the volume 1 
gallon. The solution may be worked cold or heated to 100° F., and 
with a current much stronger than that required for the platinates 
and oxalates. The ammonio (and sodio) platinic phosphates may 
be formed from the simple phosphate by carefully neutralizing 
the solution of the phosphate with ammonia (or soda) ; then add- 
ing an excess of phosphoric acid, or enough to dissolve the pre- 
cipitate formed, and an additional quantity to insure a moderate 
amount of free phosphoric acid in the bath. The phosphate 
baths will be maintained of normal strength by additions of pla- 
tinic hydrate, the solutions of which will need to be assisted by 
heating the bath, preferably at the close of each day's work. The 
metal yielded by the electrolysis of these phosphate solutions is 
brilliant and adherent. It has the same steely appearance as 
that exhibited by the oxalate solutions, but to a less pronounced 
degree. The physical properties of the deposited metal are in 
other respects like those described in connection with that ob- 
tained from the oxalate baths. 

Management of platinum baths. — Copper and brass may be 
directly coated with platinum, but iron, steel, and other metals 
have to be previously coppered ; without preliminary coppering 
these metals would soon decompose the platinum bath, indepen- 



DEPOSITION OF PLATINUM AND PALLADIUM. 279 

dent of the fact that no perfect deposit of platinum can be pro- 
duced upon them without the cementing intermediary layer of 
copper. 

Platinum baths must be used hot, and even then require a cur- 
rent of 5 to 6 volts. An abundant evolution of gas must appear 
on the objects and the anodes; the anode-surface (platinum 
anodes) must not be too small, and should be only at a few centi- 
metres distance from the objects. Since the platinum anodes do 
not dissolve, the content of platinum in the bath becomes con- 
stantly smaller, and the bath must from time to time be 
strengthened. It is then heated in a porcelain dish or enamelled 
vessel to the boiling-point, some fresh solution of sodium citrate 
is added, and platoso-ammonium chloride introduced as long as 
solution takes place. A concentrated solution of platoso-ammo- 
nium chloride may be kept at hand and a small quantity of it at 
intervals be added to the bath. 

Execution of platinizing. — The objects thoroughly freed from 
grease and pickled, and, if necessary, coppered, are suspended in 
the bath heated to between 176° and 194° F. ; this temperature 
must be kept up during the entire operation. The current should 
be of sufficient strength and the anodes placed so close to the 
objects that a liberal evolution of gas appears on the anodes. 
For platinizing large objects it is recommended to go round them, 
at a distance of 0.31 to 0.39 inch, with a hand-anode of platinum 
sheet, which should not be too small and should be connected to 
the anode-rod. When the current has vigorously acted for 8 to 
10 minutes, the objects are taken from the bath, dried, and pol- 
ished. However, for the production of heavy deposits — for 
instance, upon points of lightning-rods — the deposit is vigorously 
brushed with a steel-wire scratch-brush or fine pumice powder. 
The objects are then once more freed from grease and returned for 
10 to 15 minutes longer to the bath to receive a further deposit 
of platinum with a weaker current, which must, however, be 
strong enough to cause the escape of an abundance of gas bubbles. 
The objects are then taken out, and, after immersion in hot water, 
dried in sawdust. The deposit is then well burnished, first with 
the steel tool, and finally with the stone, whereby the gray tone 
disappears and the deposit shows the color and lustre of massive 



280 ELECTRO-DEPOSITION OF METALS. 

platinum sheet. Points of lightning-rods platinized in this man- 
ner were without flaw after an exposure to atmospheric influences 
for more than six years. 

Platinizing of glass. — Glass may be platinized by means of the 
galvanic current as follows : Dissolve 14 drachms of platinic 
hydrate in 17 J ozs. of a 10 per cent, solution of caustic soda or 
potash. Add to the solution 17J ozs. more of the alkali solution 
and dilute with water to 2 quarts. The temperature of the bath 
should not exceed 100° F., and the strength of the current should 
be 2 volts. 

Platinizing by contact. — Though a thick deposit cannot be pro- 
duced by the contact-process, Fehling's directions may here be 
mentioned as suitable for giving a thin coat of platinum to fancy 
articles. He recommends a solution of 5.64 drachms of chloride 
of platinum and 7 ozs. of common salt in 1 quart of water, which 
is made alkaline by the addition of a small quantity of soda lye, 
and for use heated to the boiling point. 

If larger articles are to be platinized by contact, free them from 
grease, and after pickling, and, if necessary, coppering, wrap them 
round with zinc wire or place them upon a bright zinc sheet and 
introduce them into the heated bath. All the remaining manipu- 
lations are the same as in other contact processes. 

Recovery of platinum from platinum solutions. — From not too 
large baths, precipitation of the platinum with sulphuretted 
hydrogen is the most suitable method and preferable to evapo- 
rating and reducing the metal from the residue. The process is 
as follows : Acidulate the platinum solution with hydrochloric 
acid, and, after warming it, conduct sulphuretted hydrogen into 
it. The metal (together with any copper present) precipitates as 
sulphide of platinum. The precipitate is filtered off, dried, and 
glowed in the air, whereby metallic platinum remains behind. 
From larger baths the platinum may be precipitated by suspend- 
ing bright sheets of iron in the acidulated bath. In both cases 
the precipitated platinum is treated with dilute nitric acid in order 
to dissolve any copper present. After filtering off and washing 
the pure platinum, dissolve it in aqua regia; the solution is then 
evaporated to dryness in the water bath, and the chloride of pla- 
tinum thus obtained may be used in making a new bath. 



DEPOSITION OF PLATINUM AND PALLADIUM. 281 

2. Deposition of Palladium. 

Properties of palladium. — Palladium, when compact, has a white 
color and possesses a lustre almost equal to that of silver. Its 
specific gravity is about 12.0; it is malleable and ductile, and 
may be fused at a white heat. In the oxybydrogen flame it is 
volatilized, forming a green vapor. It is less permanent in the 
air than platinum. It is dissolved by nitric acid ■ it is scarcely 
attacked, however, by hydrochloric or sulphuric acid ; hydriodic 
acid and free iodine coat it with the black palladium iodide. 

On account of the high price of its salts, palladium has been 
but little used for electro-plating purposes, nor, for the same 
reason, is it likely to be more extensively employed in the future. 

According to M. Bertrand, the most suitable bath consists of a 
neutral solution of the double chloride of palladium and am- 
monium, which is readily decomposed by 3 Bunsen elements 
coupled one behind the other (therefore about 5.4 volts). A 
sheet of palladium is used as anode. 

A solution of palladium cyanide in potassium cyanide does not 
yield as good results as the above. 

Palladium has of recent years been much used to plate watch 
movements. According to M. Pilet, 4 milligrammes (about -^ T 
grain) of palladium is sufficient to coat the works of an ordinary 
sized watch. M. Pilet recommends the following bath : Water 
2 quarts, chloride of palladium 5J drachms, phosphate of am- 
monia 3 J ozs., phosphate of soda, 17 J ozs., benzoic acid 2f 
drachms. This bath is suitable for all metals except zinc. 



282 ELECTRO-DEPOSITION OF METALS. 



CHAPTER XII. 

DEPOSITION OF TIN, ZING, LEAD, AND IRON. 

1. Deposition of Tin. 

Properties of Tin. — Tin is a white, highly lustrous metal ; it 
possesses but little tenacity, but has a high degree of malleability ; 
tin-foil may be obtained in leaves less than ^th of a millimetre in 
thickness. Tin melts at about 446° F. and evaporates at a high 
temperature ; the fused metal shows great tendency to crystallize 
on congealing. By treating the surface of melted tin with a 
dilute acid, the crystalline structure appears as designs {moire 
metallique), resembling the ice-flowers on frosted windows. 

Tin remains quite constant even in moist air, and resists the 
influence of an atmosphere containing sulphuretted hydrogen. 
Strong hydrochloric acid quickly dissolves tin on heating, evolv- 
ing hydrogen and forming stannous chloride. Dilute sulphuric 
a?id has but little action on the metal ; when heated with concen- 
trated sulphuric acid, sulphur dioxide is evolved. Dilute nitric 
acid dissolves tin in the cold without evolution of gas ; concen- 
trated nitric acid acts vigorously upon the metal, whereby oxide 
of tin, which is insoluble in the acid, is formed. Alkaliue lyes 
dissolve the metal to sodium stannate, hydrogen being thereby 
evolved. 

Tin baths. — The bath used by Roseleur for tinning with the 
battery works very well, and is composed as follows : I. Pyro- 
phosphate of soda 3.5 ozs., tin salt (fused) 0.35 oz., water 10 
quarts. To prepare the bath dissolve the pyrophosphate of soda 
in 10 quarts of rain-water, bring the tin-salt in a small linen bag 
into the solution, and move the bag to and fro until its contents 
are entirely dissolved. 

Objects of zinc, copper, and brass are directly tinned in this 
bath with a current of slight tension. Articles of iron and steel are 
first coppered or preliminarily tinned in a bath prepared according 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 283 

to formula "VIII., the deposit of tin being then augmented in 
bath I. with the battery current. Cast-tin anodes as large as 
possible are used, which, however, will not keep the content of 
tin in the bath constant. It is therefore necessary, from time to 
time, to add tin-salt, which is best done by preparing a solution of 
3.5 ozs. of pyrophosphate of soda in 1 quart of water and intro- 
ducing into the solution tin salt as long as the latter dissolves 
clear. Of this tin essence add to the bath more or less, as may 
be required, and also augment the content of pyrophosphate of 
soda, if, notwithstanding the addition of tin-salt, the deposition of 
tin proceeds sluggishly. 

Though the bath composed according to formula I. suffices for 
most purposes, an alkaline tin bath, first proposed by Eisner and 
later recommended by Maistrasse, Fearn, Birgham, and others, 
with or without addition of potassium cyanide, may be men- 
tioned : — 

II. Crystallized tin-salt 0.7 oz., water 1 quart, and potash lye 
of 10° Beaume until the precipitate formed dissolves. 

As seen from the formula the solution of tin-salt is compounded 
with potash lye of the stated concentration (or with a solution of 
1 oz. of pure caustic potash in water), until the precipitate of 
stannous hydrate again dissolves. 

Some operators recommend the addition of 0.35 oz. of potas- 
sium cyanide to the solution. 

Without potassium cyanide the bath requires 3.75 to 4 volts, 
and with it 3.5 volts. 

In testing Salzede's bronze bath (p. 211), it was found to yield 
quite a good deposit of tin directly upon cast-iron, and it was suc- 
cessfully used for this purpose by omitting the cuprous chloride 
and using 14.11 drachms of stannous chloride, so that the com- 
position became as follows : — 

Ha. 98 per cent, potassium cyanide 3.5 ozs., carbonate of 
potassium 35|- ozs., stannous chloride 14.11 drachms, water 10 
quarts. With 4 volts a heavy deposit was rapidly obtained. 

III. A tin bath of stannous chloride, caustic soda, and potas- 
sium cyanide, given by Pfanhauser, contains 11 J drachms of 
stannous chloride, equal to about 7| drachms of metallic tin per 



284 ELECTKO-DEPOSITION OF METALS. 

quart. It is still more advantageous to use double the quantity 
of tin, the composition of the bath being then as follows : — 

Water 10 quarts, fused stannous chloride 14 ozs., caustic soda 
17 \ ozs., 100 per cent, potassium cyanide 3 \ ozs. 

The bath, as above composed, contains about 15 drachms of 
metallic tin per quart, and with 3J volts furnishes a deposit of 
tin of about 4f grains per hour. 

Pfanhauser has recently made new experiments and found that 
still more favorable results are obtained with a solution of \\ 
ozs. of stanno-ammonium chloride in 1 quart of water, a deposit 
of 9| grains of tin per hour being obtained with a current of 
only \\ volts. 

The solution of the salt is readily effected. Cast-tin anodes are 
to be used. 

The temperature of the bath should be between 68° and 77° 
F. In case the bath becomes poor in metal, stanno-ammonium 
chloride is added. 

The deposit of tin is rather rough, but can be readily made 
bright by treatment with brass scratch-brushes. 

IV. A tin bath given by Taucher is composed as follows : 
Water 500 quarts, sodium or pyrophosphate 11 lbs., crystallized 
tin-salt 21 ozs., or, still better, fused tin-salt 17J ozs. 

Bring the water into a tank completely lined with plates or 
anodes of tin joined together and connected with the positive 
pole wire. Dissolve the pyrophosphate in the water, stirring 
constantly. Place the tin-salt in a copper-sieve, and immerse the 
latter about one-half in the solution ; an abundant milky turbid- 
ity is immediately formed, which, however, disappears on stirring. 
When all the tin-salt is dissolved, remove the sieve, and the tin- 
bath, which now forms a clear fluid, either colorless or of a 
slightly yellowish color, is ready for use, it being only necessary 
to secure the articles to be tinned to the rods connected with the 
negative pole. The anodes do not suffice to keep the bath satu- 
rated, and hence, when the deposit becomes weaker, small quanti- 
ties of equal parts of tin-salt and of sodium pyrophosphate have to 
be added. The solution of these salts should always be effected 
with the assistance of a sieve to prevent small pieces of tin-salt 
from falling to the bottom of the bath, where they would be 



DEPOSITION OF TIN, ZINC, LEAD, AND IEON. 285 

enveloped by an almost insoluble crust and remain nearly un- 
changed. 

This tin bath is suitable for all kinds of metals, the deposit 
obtained combining with considerable solidity a matted and white 
appearance closely resembling silver. 

Management of tin baths. — Tin baths should not be used at a 
temperature below 68° F. ; they require (formulae I. and II.), 
according to their composition, a current of 2 to 3 volts, so that 
two Bunsen elements coupled one after the other suffice for all 
purposes. Too strong a current causes a pulverulent reduction of 
the tin, which does not adhere well, while with a suitable current- 
strength quite a dense and reguline deposit is obtained. Cast-tin 
plates with as large a surface as possible are used as anodes. 
The choice of the tin-salt exerts some influence upon the color of 
the tinning. By using, for instance, crystallized tin-salt, which 
is always acid, in preparing the bath according to formula I., a 
beautiful white tinning with a bluish tinge is obtained, which, 
however, does not adhere as well as that produced with fused tin- 
salt. Again, the latter yields a somewhat dull gray layer of tin, 
and, therefore, the effects of the bath will have to be corrected 
by the addition of one or the other salt. 

As previously mentioned, iron and steel objects are best sub- 
jected to a light preliminary tinning by boiling in the bath VIII. ; 
however, instead of this preliminary tinning, they may first be 
electro-coppered and, after scratch-brushing the copper deposit, 
brought into the tin bath. 

When the action of the bath becomes sluggish, it has to be re- 
freshed (for formula I.) by the addition of tin salt and pyrophos- 
phate of soda, or (for formula II.) by the addition of potash lye 
and tin-salt. 

From what has been said it will be clear that the execution of 
tinning is simple enough. After freeing from grease and pickling 
the objects are brought into the bath aud tinned with a weak cur- 
rent. For heavy deposits of tin the objects are frequently taken 
from the bath, and the deposit is thoroughly brushed with a brass 
scratch-brush, not too hard, and moistened with dilute sulphuric 
acid (1 part acid of 66° Be. to 25 water), when, after rinsing in 
water, the articles are returned to the bath. If, with the use of 



286 ELECTRO-DEPOSITION OF METALS. 

too strong a current the color of the deposit is observed to turn 
a dark dull gray, scratch-brushing must be repeated. When the 
tinning is finished the articles are brushed with a brass scratch- 
brush and decoction of soap root, then dried in sawdust and 
polished with fine whiting. 

Tinning by contact and boiling. — For tinning by zinc contact 
in the boiling tin bath the following solutions may be recom- 
mended : — 

V. According to Gerhold : Pulverized tartar and alum, of 
each, 3.5 ozs., fused stannous chloride 14 drachms, rain-water 
10 quarts. 

VI. According to Roseleur : Potassium pyrophosphate 7 ozs., 
crystallized stannous chloride (tin-salt), 11 drachms, fused stan- 
nous chloride 2.8 ozs., rain-water 10 quarts. 

VII. According to Roseleur, for tinning by immersion : Potas- 
sium pyrophosphate 5.6 ozs., fused stannous chloride 1.23 ozs., 
rain-water 10 quarts. 

Formulae V. and VI. yield good results. For tinning by con- 
tact, heat the bath to boiling and suspend the clean and pickled 
objects in contact with pieces of zinc, or, better, wrapped around 
with zinc wire spirals, care being had from time to time to shift 
them about to prevent staining. Large baths which cannot be 
readily heated are worked cold, the objects being covered with a 
large zinc plate; in the cold bath the formation of the tin deposit 
requires, of course, a longer time. By using the electric current 
the deposit can be made as heavy as desired. By immersion in 
the bath prepared according to formula VII. zinc can only be 
coated with a very thin film of tin, which, however, can be made 
as heavy as desired by the use of a battery. 

For tinning by contact in a cold bath, Zilken has patented the 
following solution: Dissolve with the aid of heat in 100 quarts 
of water, tin-salt 7 to 10.5 ozs., pulverized alum 10.5 ozs., com- 
mon salt 15f ozs., and pulverized tartar 7 ozs. The cold solution 
forms the tin bath. The objects to be tinned are to be wrapped 
round with strips of zinc. Duration of the process 8 to 10 
hours. 

Tinning solution for iron and steel articles. — VIII. Crystallized 
ammonium-alum 7 ozs., crystallized stannous chloride 2.8 drachms, 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 287 

fused stannous chloride 2.8 drachms, rain-water 10 quarts. Dis- 
solve the ammonium-alum in the hot water, and when dissolved 
add the tin-salts. The bath is to be used boiling hot and kept 
at its original strength by an occasional addition of tin-salt. The 
clean and pickled iron objects, being immersed in the bath, 
become in a few seconds coated with a firmly adhering film of 
tin of a dead 'white color, which may be polished by scratch- 
brushing or scouring with sawdust in the tumbling drum. Tin- 
ning by boiling in this bath is the most suitable preparation for 
iron and steel objects, which are to be provided with a heavy 
electro-deposit of tin. To be entirely sure of success it is recom- 
mended thoroughly to scratch-brush the objects, then to return 
them once more to the bath, and finally to suspend them in a bath 
composed according to formula I. or II. 

A tinning solution for small brass a.nd copper articles (pins, eyes, 
hooks, etc.) consists of a boiling solution of: Pulverized tartar 
3.5 ozs., stannous chloride (tin-salt) 14.11 drachms, water 10 
quarts. After heating the bath to the boiling-point immerse the 
objects to be tinned in a tin sieve or in contact with pieces of 
zinc ; frequent stirring with a tin rod shortens the process. 

Another solution, given by Bottger, also yields good results. 
Dissolve oxide of tin by boiling with potash lye, and place the 
copper or brass objects to be tinned in the boiling solution in 
contact with tin shavings. 

Eisner's bath yields equally good results. It consists of a 
solution of equal parts of tin-salt and common salt in rain-water. 
The manipulation is the same as given above. 

A durable coating of tin is also produced with the use of potas- 
sium stannate, which is prepared as follows : Tin is melted and 
then granulated by pouring it into water. The granulated tin is 
brought into a vessel of glass or porcelain and crude nitric acid 
poured over it, whereby, with strong effervescence of the fluid 
and the evolution of brown-red vapors, it is converted into a 
white powder consisting of stannic oxide. The latter is separated 
from the unchanged tin by washing with water, and dried. The 
dry powder is mixed with pure potash in the proportion of 3 
parts stannic oxide and 4 parts potash. The mixture is melted 
in an iron crucible and the fused mass poured upon a stone-slab. 



288 ELECTRO-DEPOSITION OF METALS. 

It consists of potassium starmate and is dissolved in boiling 
water. Potassium stannate may also be prepared by adding to 
a solution of tin-salt in water aqua ammonia as long as a precipi- 
tate is formed. The mass is then allowed to drain off upon a 
linen cloth and repeatedly washed with water. The residue, con- 
sisting of stannous hydrate, is boiled with strong potash lye and 
the solution of potassium stannate thus obtained diluted with 
water. 

The tinning of needles is effected by spreading them out upon 
a sieve and immersing the latter in the bath ; larger articles are 
touched with a tin-rod while in the bath. The temperature of 
the bath should be between 122° and 212° F. Larger articles of 
brass or bronze are best coppered previous to tinning, which is 
effected by wrapping them with iron wire and immersing them in 
dilute sulphuric acid for a short time; hydrochloric acid may be 
substituted for the sulphuric acid. 

Tinning may also be effected by dissolving 1 part tin-salt in 
10 parts water, adding to the solution one of 2 parts of caustic 
potash in 20 of water and stirring until the fluid is clear. The 
articles to be tinned are placed upon a tin-plate. The latter is 
brought into the hot bath and touched on several places with 
tin-rods. 

To give articles of brass, copper, or iron a thin, superficial 
coating of tin, dip them in a solution of tin-salt in which granulated 
tin has been lying for some time, then dust them with tin-powder, 
rub them with a woollen rag, and repeat the operation until the 
article appears tinned. 

A characteristic method of tinning by Stolba is as follows: 
Prepare a solution of 1.75 ozs. of tin-salt and 5.64 drachms of 
pulverized tartar in 1 quart of water ; moisten with this solution 
a small sponge and dip the latter into pulverulent zinc. By 
then rubbing the thoroughly cleansed and pickled articles with 
the sponge they immediately become coated with a film of tin. 
To obtain uniform tinning, the sponge must be repeatedly dipped 
now into the solution and then into the zinc-powder, and the rub- 
bing;: continued for a few minutes. 

For coloring and platinizing tin, see special chapter. 



DEPOSITION OF TIN, ZINC, LEAD, AND IKON. 289 

2. Deposition of Zinc. 

Properties of zinc. — Zinc is a bluish-white metal possessing 
high metallic lustre. It melts at 770° F. At the ordinary 
temperature zinc is brittle, but is malleable at between 212° and 
300° F., and can be rolled into sheets ; at 392° F. it again be- 
comes brittle and may be readily reduced to powder. The specific 
gravity of zinc varies from about 6.86 to 7.2. When strongly 
heated in air or in oxygen it burns with a greenish-white flame, 
producing dense white fumes of the oxide. 

In the air, zinc loses its lustre and becomes coated with a gray 
layer of oxide, which protects the metal beneath from further 
oxidation. Pure zinc dissolves slowly in the ordinary mineral 
acids, but the commercial article containing foreign metals is 
rapidly attacked with evolution of hydrogen. 

Zinc being a very electro-positive metal precipitates most of 
the heavy metals from their solutions, especially copper, silver, 
lead, antimony, arsenic, tin, cadmium, etc., this being the reason 
why in dissolving impure zinc the admixed metals do not pass 
into solution so long as zinc in excess is present. Caustic alkalies 
also dissolve zinc with formation of an oxide and free hydrogen, 
especially when it is in contact with a more electro-negative 
metal. 

Zinc baths. — Though most metals can be readily coated with 
a firmly adhering thin layer of zinc by the wet way and with 
the aid of the battery, electro-deposited zinc in comparison with 
that deposited by "galvanizing" is much inferior as a protective 
coating. It may, nevertheless, be useful to give the composition 
of some baths which have stood the test, as well as the most ap- 
proved directions for zincking. 

I. Sulphate of zinc (white vitriol) 2.8 ozs., ammonium sul- 
phate If ozs., sal ammoniac 11 drachms, water 1 quart. Dissolve 
the salts in the heated water and use the bath at 68° F. The 
current-strength should only be slightly greater than necessary 
for the decomposition of the bath ; the current of two Bunsen 
elements coupled one after the other is quite too strong, and 
must, therefore, be correspondingly weakened by the resistance- 
board. 

19 



290 ELECTRO-DEPOSITION OF METALS. 

As anodes rolled zinc sheets of not too small dimensions are to 
he used. This bath is suitable for heavily zincking objects (sheets 
and plates) of wrought- and cast-iron, steel, and all other metals, 
but not for zincking hollow articles if anodes cannot at equal dis- 
tances be placed around them. The most suitable tension is 2.8 
to 3 volts. 

II. Caustic potash 2 ozs., chloride of zinc 5J drachms, sal am- 
moniac 11 drachms, water 1 quart. Dissolve the caustic potash 
in one-half of the water, and the chloride of zinc and sal ammo- 
niac in the other half, and mix the solution with stirring. The 
result is a clear fluid which requires a current of 2.5 to 3 volts 
for its decomposition. Zinc sheets are also used as anodes. 
In this bath the deposit upon hollow objects proceeds better 
than in the preceding, though frequent turning of the articles 
is necessary. 

III. Alum 3J ozs., hydrated oxide of zinc 5| drachms, water 
1 quart. Dissolve 14 drachms of sulphate of zinc in 1 pint of 
water and carefully add potash lye until a further drop of it no 
longer produces a precipitate. Since potash lye dissolves the 
hydrated oxide of zinc an excess has to be avoided. The pre- 
cipitate is filtered off, washed with water, and the hydrated oxide 
of zinc, while still moist, is heated together with the solution of 
3£ ozs. of alum in 1 quart of water, whereby it is completely dis- 
solved. This bath requires a current of 3 to 3.5 volts. 

IV. Sulphate of zinc (white vitriol) 2.8 ozs., water 1 quart, 
and potash lye sufficient to redissolve the precipitated hydrated 
oxide of tin. This bath also works quite well, and requires from 
2.75 to 3 volts and 1.5 amperes per 15 J square inches. 

Solution of cyanide of zinc in potassium cyanide may also be 
used for zincking, such a bath having been warmly recommended 
by some authors. However, the production of deposits of some 
thickness requires a long time, and the deposit itself shows a ten- 
dency to peeling off. 

Execution of zincking. — Next to thorough cleansing and pick- 
ling the objects, especially iron castings, and regulating the cur- 
rent, electro-zincking depends on the frequent turning and 
changing of the objects in the bath, since the deposit is chiefly 
formed upon the portions nearest to the anodes, and not at all, or 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 291 

with difficulty, upon the portions away from the anodes. If, not- 
withstanding frequent changing, some portions do not acquire a 
deposit, recourse must be had, as in nickelling, to the hand anode. 
Next to frequently changing the articles in the bath, it is recom- 
mended to scratch-brush them several times, especially if heavy 
deposits are to be produced. It is also advisable to somewhat 
heat the baths, if possible. 

It is of advantage to superficially zinc iron objects by a com- 
bined process of contact and boiling, and then to augment the 
layer of zinc in the bath. 

After thorough scratch-brushing with a steel brush, not too 
hard, and a decoction of soap-root, the zincked objects are rinsed 
in lime-water, then plunged into hot water, and dried in saw- 
dust; polishing is effected upon soft cloth bobs with Vienna lime 
and oil. 

For zincking iron by contact quite a concentrated solution of 
chloride of zinc and sal ammoniac in water, only, is suitable, in 
which the objects are placed in contact with large surfaces 
of zinc. 

To coat brass and copper with a bright layer of zinc proceed 
as follows : Boil commercial zinc-gray, i. e., very finely divided 
metallic zinc, several hours with concentrated solution of caustic 
soda. Then immerse the articles to be zincked in the boiling 
fluid, when, by continued boiling, the articles will in a short time 
become coated with a very bright layer of zinc. When a copper 
article thus coated with zinc is carefully heated in an oil bath to 
between 248° and 284° F., the zinc alloys with the copper, form- 
ing a sort of bronze similar to tombac. 

Weil zincks copper and coppered objects by immersing them 
in a boiling concentrated solution of caustic potash in contact 
with zinc. The coating thus obtained is said to be adherent and 
brilliant. 

For coloring and platinizing zinc, see special chapter. 

Zinc alloys. — The production of the principal zinc alloy, brass, 
by the galvanic method, having already been mentioned, and also 
that of a zinc-nickel-copper alloy (German silver), it remains to 
give an alloy of zinc with tin which can be produced by the use 
of the battery. 



292 ELECTKO-DEPOSITTON OF METALS. 

A suitable bath for depositing this alloy consists of: Chloride 
of zinc 6f drachms, crystallized stannous chloride 9 drachms, 
pulverized tartar 9 drachms, pyrophosphate of soda 2f drachms, 
water 1 quart. Dissolve the salt at a boiling heat, and filter the 
cold solution, when it is ready for use. For anodes, cast plates of 
equal parts of tin and zinc are used. 

3. Deposition of Lead. 

The properties of lead only interest us in so far as it being less 
attacked by most mineral acids than other metals, objects have 
been coated with it in order to protect them against the action of 
such agents. For decorative purposes electro-deposits of lead are 
not used, and those as a protection against chemical influences can- 
not be produced of sufficient thickness for that purpose. 

Lead baths. — I. Dissolve, by continued boiling, caustic potash 
1.75 ozs. and finely pulverized litharge 0.17 oz. in 1 quart of 
water. 

II. According to Watt, the following solution is used : Acetate 
of lead 0.17 oz., acetic acid 0.17 oz., water 1 quart. 

The bath prepared according to formula I. deserves the pref- 
erence. 

Lead baths require anodes of sheet-lead or cast-lead plates, a 
very weak current, and in order to produce a dense deposit of some 
thickness the objects have to be frequently scratch-brushed. Iron 
is best previously coppered. Superoxide of lead being separated 
upon the anodes, they have to be frequently cleansed with a scratch- 
brush. The formation of superoxide of lead is utilized for the 
production of the so-called Nobili's rings (electrochromy), which 
will be mentioned below. 

To coat gun-barrels and other articles of steel or iron with super- 
oxide of lead as a protection against rust, suspend the bright articles 
as anodes in a solution of nitrate of lead mixed with ammonium 
nitrate. 

Leading by contact is effected by suspending the objects, 
thoroughly freed from grease, in the boiling solution prepared 
according to formula I., in contact with a piece of tin. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 293 

Nobili's rings (iridescent colors, electrochromy). — The separation 
of superoxide of lead upon the anodes or upon objects suspended 
as anodes, produces superb effects of colors. For the production 
of such colors, a bath is prepared by boiling for half an hour 
3| ozs. of caustic potash, 14 drachms of litharge, and 1 quart of 
water. The operation is as follows : Suspend the articles, care- 
fully freed from grease and pickled, to the anode-rods, and with 
a weak current introduce in the lead solution a thin platinum 
wire connected with the object-rod by flexible copper wire with- 
out, however, touching the article. The latter will successively 
become colored with various shades — yellow, green, red, violet, 
and blue. By the continued action of the current, these colors 
pass into a discolored brown, which also appears in the begin- 
ning if the current is too strong, or the platinum wire be immersed 
too deep. Such unsuccessful coloration has to be removed by 
rapidly dipping in aqua fortis, and, after rinsing in water, suspend- 
ing the article in the bath. For coloring not too large surfaces, 
a medium-sized Bunsen element is, as a rule, sufficient, if the 
platinum wire be immersed about f inch. 

Colors of all possible beautiful contrasts may be obtained by 
perpendicularly placing between the objects to be colored and the 
platinum wire a piece of stout parchment paper, or providing 
the latter with many holes or radial segments. 

4. Deposition of Iron (Steeling). 

The principal practical use of the electro-deposition of iron is 
to cover printing plates of softer metals with a coating of " steel," 
to increase their wearing qualities. The steeling of printing 
plates, however, has no advantage over nickelling or cobalting, 
which has lately been introduced with the best success. 

Steel baths. — I. According to Varrentrapp : Pure green vitriol 
4f ozs., sal ammoniac 3 J ozs., water 1 quart. Boil the water 
for | hour to remove all air, and, after cooling, add the green 
vitriol and sal ammoniac. By the action of the air, and the 
oxygen appearing on the anodes, this bath is readily decomposed, 
insoluble basic sulphate of iron being separated as a delicate 
powder, which has to be frequently removed from the fluid by 



294 ELECTRO-DEPOSITION OF METALS. 

filtering. To decrease decomposition, the double sulphate of iron 
and ammonium, which can be more readily obtained pure and free 
from oxide, may be used. 

II. Sal ammoniac 3 \ ozs., water 1 quart. This neutral solu- 
tion of sal ammoniac may be made into an iron bath by hanging 
in it iron sheets as anodes, suspending an iron or copper plate 
as cathode, and allowing the current to circulate until a regular 
separation of iron is attained, which is generally the case in 5 to 
6 hours. Although a separation of hyd rated oxide of iron also 
takes place in this bath, it is in a less degree than in that pre- 
pared according to formula I. For the production of not too 
heavy a deposit of iron, some operators claim to have obtained 
the best results with this bath. 

For the 'production of electrotypes in iron the following baths 
(III. and IV.) are most suitable : — 

III. Ammonio-ferrous sulphate If ozs., water 1 quart. The 
solution must be kept absolutely neutral, which according to 
Klein's suggestion is, on the one hand, to be attained by the use 
of large anode-surfaces, and, on the other, by suspending in the 
bath a copper plate and connecting it with the anodes. It would 
seem more advantageous to maintain the neutrality of the bath 
by suspending in it small bags filled with carbonate of magnesia. 

A steel bath highly recommended by Klein consists of a solu- 
tion of equal parts of green vitriol and sulphate of magnesia, 
which is kept neutral by bags filled with carbonate of magnesia 
suspended in the fluid. The most suitable concentration of the 
solution corresponds to a specific gravity of 1.55 ; and according 
to the most recent experiments, the current-density should at the 
utmost amount to 0.02 ampere per 15J square inches, with a 
distance of 1J inches of the anodes from the plate, this distance 
to be gradually increased. 

For steeling his copper printing plates, which are frequently 
of quite large dimensions, C. Obernetter of Munich employs the 
following method : The plate to be steeled is first freed from all 
color, which is best effected by means of chloroform or oil of tur- 
pentine. It is then thoroughly washed and brushed by means of a 
bristle-brush with potash lye or a solution of 1 part potassium 
cyanide in 20 parts water, and again washed. In this state the 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 295 

plate is suspended to the cathode of the steeling bath. A clean 
steel plate serves as anode. Both the anode and cathode are in a 
horizontal position. Bubbles forming on the cathode are readily 
removed by means of a feather. In about five minutes the plate 
is thoroughly steeled. 

The iron bath consists, according to Obernetter, of ferrous sul- 
phate 30 parts by weight, iron-alum 30, sal ammoniac 60, dis- 
solved in warm distilled water 1000. 

The solution is allowed to stand for two days, and is then 
filtered twice. It should also be filtered every time before use. 

After steeling, the plate is cleansed in the above described man- 
ner, and oiled to prevent rusting. 

When during the operation of printing the deep places of the 
plate commence to become red, i. e., when the copper shines 
through, the steeled plate may be re-steeled, but, according to 
Obernetter, this should not be done more than once. It is best 
in every case to first remove the old steeling with dilute sulphuric 
or nitric acid, and then to re-steel the plate. 

According to Obernetter' s statements, 21,000 copies were printed 
from a plate thus steeled without the plate suffering any injury, 
the last impression being in every respect equal to the first. 

For decorative purposes, a deep black deposit of iron may, 
according to "La Metal lurgie," be produced as follows : Dissolve 
as large a quantity of steel filings as possible in 50 quarts of com- 
mercial hydrochloric acid. The saturation of the solution is 
recognized by a sediment, which no longer dissolves, being formed 
on the bottom of the vessel. Then add 2 lbs. of white arsenic, 
and vigorously stir the mixture. The arsenic dissolves very 
slowly, but the bath cannot be considered finished until all of it 
is dissolved, and the color obtained by means of the bath is the 
deeper the more complete the solution of the arsenic. The 
articles to be treated are connected to the negative pole of the 
battery, iron and carbon plates serving as anodes. For a bath of 50 
quarts, two Bunsen elements about 7f inches high are required, and 
the bath being very acid, the articles must be connected with the 
battery prior to immersion. Upon copper and brass the deposit 
is directly produced, but iron articles being attacked by the bath, 
are first provided with a coat of nickel. The deposit of iron upon 



296 ELECTRO-DEPOSITrON OF METALS. 

this nickel coating is very beautiful, and has been designated as 
"black nickelling." The coating must, of course, be protected 
from oxidation by a colorless lacquer. 

Management of iron baths. — As previously mentioned, the insol- 
uble precipitate from time to time formed in the bath has to be 
removed by filtration. This precipitate is, however, very delicate, 
and when stirred up might settle upon the objects and prevent 
the adherence of the deposit. It is, therefore, advisable to use 
for steel baths, vats of much greater depth than correspond to 
the height of the objects, whereby the stirring up of the sediment 
in suspending the objects in the bath is best avoided. The baths 
must be kept thoroughly neutral, which may be effected in vari- 
ous ways. One method has already been mentioned in connec- 
tion with formula III. ; another method, which has been used 
with decided success, consists in precipitating, excluding the air 
as much as possible, a solution of pure green vitriol with ammo- 
nium carbonate, quickly filtering off the ferrous carbonate, wash- 
ing the latter once or twice in cold water previously boiled, 
stirring it while moist into the bath, and allowing it to settle 
for one hour. 

Execution of steeling. — Only the manipulations for the produc- 
tion of thin deposits will here be discussed. The production of 
heavy galvanoplastic deposits of iron will be explained later on 
under " Galvanoplasty." 

The clean and pickled objects are coated in the baths accord- 
ing to formulae I. and II. with a current of 1 to 1.25 volts, and 
the anodes at a distance of 3| to 4| inches, after which the cur- 
rent is reduced to 0.75 or 1 volt. To produce iron deposits of 
any kind of thickness, the escape of the hydrogen bubbles which 
settle on the objects must be promoted by frequent blows with 
the finger upon the object-rod. As anodes, iron sheets of a large 
surface freed from scale by pickling are to be used. When steel- 
ing is finished, the articles are thoroughly rinsed, then plunged 
into very hot water, and, after drying in sawdust, placed for 
several hours in a drying chamber heated to about 212° F., to 
expel all moisture from the pores. 

Steeling by contact is readily effected by touching the objects 
with zinc, best in a bath prepared according to formula I. 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 297 



CHAPTER XIII. 

DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 

1. Deposition of Antimony. 

Properties of antimony. — Electro-deposited antimony possesses 
a gray lustre, while native, fused antimony shows a silver-white 
color. Antimony is hard, very brittle, and may easily be reduced 
to powder in a mortar. It melts at 842° E., and at a strong red 
heat takes fire and burns with a white flame, forming the trioxide. 
Its density is 6.8. It is permanent in the air at ordinary temper- 
atures. Cold, dilute, and concentrated sulphuric acid have no 
effect upon antimony, but the hot concentrated acid forms sul- 
phide of antimony. By nitric acid the metal is more or less 
energetically oxidized, according to the strength and temperature 
of the acid. 

Antimony baths. — Electro-depositions of antimony are but sel- 
dom made use of in the industries, though they are very suitable 
for the production of contrasts in decorating. Gore discovered 
the explosive power of depositions of antimony chloride, or of 
antimony containing hydrochloric acid. According to Gore, a 
bath consisting of tartar emetic 3 ozs., hydrochloric acid 4^ ozs., 
tartaric acid 3 ozs., and water 1 quart, yields a gray crystalline 
deposit of antimony. This bath requires a current of about 3 
volts. The deposit possesses the property of exploding when 
scratched with a hard object. The explosion of the deposit is 
caused by a content of chloride of antimony. Bottger found 3 
to 5 per cent, of chloride of antimony in the deposit, and Gore 
6 per cent. A similar explosive deposit is obtained by electro- 
lyzing a simple solution of chloride of antimony in hydrochloric 
acid (liquid butter of antimony, liquor stibii chlorati) with the 
current. 

A lustrous non-explosive deposit of antimony is obtained by 
boiling 4.4 ozs of carbonate of potash, 2.11 ozs. of pulverized 



298 ELECTRO-DEPOSITION OF METALS. 

antimony sulphide, and 1 quart of water, for 1 hour, replacing 
the water lost by evaporation, and filtering. Use the hath 
boiling hot, employing cast antimony plates or platinum sheets 
as anodes. 

Another antimony bath may be prepared by dissolving fresh lv 
precipitated sulphide of antimony with an excess of sulphide of 
ammonia. It yields a very lustrous and adherent deposit of anti- 
mony, which, in 6 to 8 minutes, is of sufficient thickness to hear 
polishing with Vienna lime upon rapidly revolving cloth wheels. 
An unpleasant feature of this bath is that during the plating pro- 
cess much sulphur is separated, which renders the bath turbid, 
so that it has to be frequently filtered. With the use of platinum 
anodes, this separation of sulphur is, of course, still greater than 
with antimony anodes. 

2. Deposition of Arsenic. 

Properties of arsenic. — Arsenic has a gray-white color, a strong 
metallic lustre, is very brittle, and evaporates at a red heat. In 
dry air arsenic retains its lustre, but soon turns dark in moist 
air. It is scarcely attacked by dilute hydrochloric and sulphuric 
acids, while concentrated sulphuric acid as well as nitric acid 
oxidizes it to arsenious acid. If caustic alkalies are fused together 
with arsenic, a portion of the latter is converted into alkaline 
arsenate. 

Arsenic baths. — Deposits of arsenic are more frequently used 
than antimony deposits for decorative purposes ; for instance, to 
color gray the dead background of brassed lamp-legs, vases, etc., 
while the prominent portions are bright brass. A solution suit- 
able for depositing arsenic upon all kinds of metals is as follows : — 

I. Pulverized arsenious acid If ozs., crystallized pyrophosphate 
of soda 0.7 oz., 98 per cent, potassium cyanide If ozs., water 1 
quart. 

Dissolve the pyrophosphate of soda and potassium cyanide in 
the cold water, and after adding, with stirring, the arsenious acid, 
heat until the latter is dissolved. In heating, fumes containing 
prussic acid escape, the inhalation of which must be carefully 
avoided. The bath is used warm, and requires a vigorous cur- 



DEPOSITION OF ANTIMONY, AESENIC, ALUMINIUM. 299 

rent of at least 4 volts, so that, at the least, 3 Bunsen elements 
have to be coupled for tension. After suspending the objects 
they are first colored black-blue, the color passing with an in- 
creased thickness of the deposit into pale blue, and finally into 
the true arsenic gray. Platinum sheets or carbon plates are to be 
used as anodes. 

Instead of a bath prepared according to formula I., a solution 
of the following composition may be used : — 

II. Sodium arsenate If ozs., 98 per cent, potassium cyanide 
0.8 oz., water 1 quart. Boil the solution for half an hour, then 
filter and use it at a temperature of at least 167° to 176° F., 
with a strong current ; it yields a good deposit. 

Large baths, to be used cold, must be more concentrated, and 
require a stronger current than hot baths. 

When the baths begin to work irregularly and sluggishly, they 
have to be replaced by fresh solutions. 

In the execution of deposits of arsenic and antimony the same 
rules are to be observed as for the other electro-plating processes. 

Djposits of antimony and arsenic by contact and immersion are 
much used for coloring brass and copper, as well as iron (brown- 
ing of gun-barrels) and silver. Most frequently a warm solution 
of antimony trichloride (the butter of antimony of commerce) 
in hydrochloric acid is used for this purpose, in which the clean 
and pickled brass articles acquire a coating of a steel-gray color 
with a bluish tinge. By using instead a hot mixture of chloride 
of arsenic with a small quantity of water, a steel-gray color with- 
out a bluish tinge is obtained. 

By immersing brass in a solution of 20 parts by weight of 
arsenious acid, 40 of hydrochloric acid, 800 of water, and 10 of 
sulphuric acid heated to between 122° and 140° F., it becomes 
black by the separation of pulverulent arsenic ; after rinsing in 
water and drying the coat adheres quite well. By contact with 
zinc the deposit is obtained in a shorter time and adheres better. 

3. Deposition of Aluminium. 

Properties of aluminium. — Aluminium is a white, silvery metal 
with an almost imperceptible bluish tinge. It is extremely light, 



300 ELECTRO-DEPOSITION OF METALS. 

the specific gravity being only 2.58, is very malleable and ductile, 
takes a high polish, and is not liable to tarnish in the air. It 
melts at about 1300° F. Its principal common impurities are 
iron and silicon. 

Aluminium baths. — Aluminium does not seem to possess any 
qualities that would make it advantageous as an electro-deposit 
upon other metals. Many solutions have been proposed which it 
was claimed should give good deposits of the metal, but have been 
found by various experimenters to be worthless. We therefore 
confine ourselves to giving only a few solutions which are claimed 
to give good results. 

I. Bertrand states that he has deposited aluminum upon a plate 
of copper in a solution of the double chloride of aluminium and 
ammonium by using a strong current from three Bunsen elements, 
the bath being worked at 140° F. 

II. Goze's process. — Mr. Goze obtained a deposit of aluminium, 
by the single-Cell method from a dilute solution of the chloride. 
The liquid was placed in a jar in which was immersed a porous 
cell containing dilute sulphuric acid ; an amalgamated zinc plate 
was immersed in the acid solution and a plate of copper in the 
chloride solution, the two metals being connected by a copper 
conducting wire. At the end of some hours the copper plate 
became coated with a lead-colored deposit of aluminium, which, 
when burnished, presented the same degree of whiteness as 
platinum and did not appear to tarnish readily when immersed 
in cold water or exposed to the atmosphere, but was acted upon 
by dilute sulphuric and nitric acids. 

III. The following formula is given by Mr Herman Reinbold, 
who states that it yields excellent results : Dissolve 50 parts by 
weight of alum in 300 of water and to this add 10 parts of 
aluminium chloride. The solution is to be heated to 200° F., 
and, when cold, 39 parts of potassium cyanide are to be added. 
A feeble current should be used. 

IY. A new method for the electro-deposition of aluminium is 
as follows :* To a 20 per cent, solution of ammonium-alum in 
warm water add a solution of about the same quantity of pearl- 

* Neueste Erfindungen und Erfahrungen, vol. xix. p. 353. 



G ALVA NOPL AST Y. 301 

ash and of a small quantity of ammonium carbonate. The mix- 
ture effervesces and yields a precipitate, which is filtered off and 
thoroughly washed with water. Over the precipitate thus obtained 
pour a warm solution of 16 per cent, ammonium-alum and 8 per 
cent, pure potassium cyanide, and boil the whole in a closed iron 
vessel for 30 minutes. The proper proportions for the solutions 
are as follows: Fii'st alum solution: Ammonium-alum 4 lbs., 
warm water 10 quarts. Pearl-ash solution: Pearl-ash 4 lbs., 
warm water 10 quarts, ammonium carbonate 4J to 5| drachms. 
Second alum solution: Ammonium-alum 8 lbs., warm water 25 
quarts, potassium cyanide 4 lbs. Then add 20 quarts of water 
and about 4 lbs. more of potassium cyanide, and let the whole 
boil for about \ hour. The filtered solution is then ready for use 
as the electrolytic bath. As anodes perforated aluminium plates 
are used, which can be raised and lowered. The cathodes receive 
the deposit. The bath is maintained at a temperature of between 
80° and 149° F. By adding pieces of other metals, such as 
gold, silver, nickel, copper, etc., to the aluminium anodes the 
color of the deposit may be somewhat changed. If the deposit 
shows a gray coloration it is made lustrous by dipping in a solu- 
tion of caustic soda, which also prevents oxidation. 

The electro-deposition of tungsten, cadmium, and bismuth 
having, up to the present time, attained no practical importance, 
its discussion may be omitted. 



CHAPTER XIV. 

GALVANOPLASTY (REPRODUCTION). 

By galvanoplasty proper is understood the production, with the 
assistance of the electric current, of copies of articles of various 
kinds, true to nature, and of sufficient thickness to form a resist- 
ing body, which may be separated from the object serving as a 
mould. 

Copper is the most suitable metal for galvanoplastic processes, 
that which is precipitated by electrolysis showing the following 



302 ELECTRO-DEPOSITION OF METALS. 

valuable properties : It may be precipitated chemically pure, and 
in this state is less capable of change than ordinary commercial 
copper or the ordinarily used copper alloys, its strength of 
extension being 20 per cent, greater than that of melted copper ; 
its hardness is also greater than that of melted copper, while 
its specific gravity (8.85) lies between that of cast and rolled 
copper. 

The physical properties of copper deposited by electrolysis are 
dependent on the condition of the bath as well as on the intensity 
and tension of the working current. The bath used for precipi- 
tating the copper is in all cases a solution of blue vitriol. Smee 
had originally proved by experiments that copper is obtained as a 
more tenacious and fine-grained deposit when the current-strength 
is as great as possible, without, however, evolution of hydrogen 
taking place ; while copper in pulverulent, sandy form is obtained 
with a current-strength that liberates hydrogen, and in coarsely 
crystalline form when the current strength is very slight. 

At a more recent period, von Hiibl instituted a series of 
systematic experiments for the determination of the conditions 
under which deposits with different physical properties are ob- 
tained. Hiibl worked with 5 per cent, neutral, and 5 per cent, 
acid, solutions of copper, as well as with 20 percent, neutral, and 
20 per cent, acid solutions. The neutral solutions were prepared 
by boiling blue vitriol solution with carbonate of copper in ex- 
cess, and the acid solutions by adding 2 per cent, of sulphuric acid 
of 66° Be\ The result was that in the neutral 5 per cent, solu- 
tions less brittle deposits were obtained with a small current- 
density than in a more concentrated solution, though the appear- 
ance of the deposits was the same. The experiments with acid- 
ulated baths confirmed the fact that free sulphuric acid promotes 
the formation of very fine-grained deposits even with very slight 
current-densities, and it appears that the brittleness of copper de- 
posited from acid baths is influenced less by the concentration 
than by the current-density used. 

The processes used in galvanoplasty may be arranged in two 
classes, viz., the deposition of copper with or without the use of 
external sources of current, the first comprising galvanoplastic 



GALVANOPLASTY. 



303 



deposits produced by means of the single-cell apparatus, and the 
other those by the battery or dynamo-machine. 

1 . Galvanoplastic Deposition in the Cell Apparatus. 

The cell apparatus consists of a vessel containing blue vitriol 
solution kept saturated by a few crystals of blue vitriol placed in 
a muslin bag or a small perforated box of wood, stoneware, etc. 
In this vessel are placed round or square porous clay cells (dia- 
phragms) which contain dilute sulphuric acid and a zinc plate, the 
zinc plates being connected with each other and with the objects 
to be moulded — which may be either metallic or made conductive 
by graphite — by copper wire or copper rods. The objects to be 
moulded play the same role as the copper electrode in a Daniell 
element, and the cell apparatus is nothing else but a species of 
Daniell element in which the internal, instead of an external, cur- 
rent is utilized. As soon as the circuit is closed by the contact of 
the objects to be moulded with the zinc of the porous cell, the 

Fig. 118. 




electrolytic process begins ; the zinc is oxidized by the oxygen and 
with the sulphuric acid forms zinc sulphate (white vitriol), while 
the copper is reduced from the blue vitriol solution and deposited 
in a homogeneous layer upon the articles to be moulded. 



304 



ELECTRO-DEPOSITION OF METALS. 



A simple apparatus, frequently used by amateurs for moulding 
medals, reliefs, etc., is shown in Fig. 118. 

In a cylindrical vessel of glass or stoneware filled with satu- 
rated blue vitriol solution is placed a porous clay cell, and in the 
latter a zinc cylinder projecting about 0.039 to 0.079 inch above 
the porous clay cell. To the zinc is soldered a copper ring, as 
plainly shown in the illustration. The clay cell is filled with 
dilute sulphuric acid (1 acid to 30 water), to which some amalga- 
mating salt may be suitably added. The articles to be moulded 
are suspended to the copper ring, care being had to have the 
surfaces which are to be covered near and opposite to the cell. 
To supplement the content of copper, small linen or sail-cloth 
bags filled with blue vitriol are attached to the upper edge of the 
vessel. 

Fig. 119 shows another form of cell-apparatus which is much 
used in printing establishments for the production of cliches. 

Fig. 119. 




A is a large box lined with gutta-percha. In this box is sus- 
pended a smaller box, B, the bottom of which is formed of a disk 
of leather or parchment. To the side of this box are nailed strips, 6. 
To these strips is secured a piece of stout linen, which serves par- 
tially as a support of the zinc plate Z n and partially to prevent 
impurities of the zinc from falling upon the leather disk. The 
zinc plate is connected with the strap K, which is made of sheet 
copper. In the box A lies the board D, which is sufficiently 
■weighted with strips of lead to prevent it from floating in the fluid. 
To prevent the separation of copper, these lead strips are coated 



GALVANOPLASTY. 305 

with a varnish made from sealing-wax or with gutta-percha. To 
the upper side of the board is nailed the copper strap K', which 
is insulated as far as it touches the fluid and the board by a 
coating of gutta-percha. The binding screw E connects the two 
copper straps. A perforated copper sheet bent in the form of a 
gutter dips above in the copper solution. During the operation 
this copper sheet is kept filled with crystals of blue vitriol, and 
serves to maintain a uniform saturation of the fluid. 

To produce deposits with this apparatus, the first matrice is 
laid upon the portion of copper strap upon the board D. The 
copper strap is then connected with the conducting surface by 
driving a brass pin through the matrice and the strap into the 
board. Underneath the other end of the matrice is placed a 
small piece of copper sheet insulated by gutta-percha, so that it 
projects \ to f inch beneath the matrice. It is also brought in con- 
tact with the conducting surface by means of a brass pin. Upon 
this sheet is placed the second matrice, which is also secured with 
a brass-pin, and so on, until all the moulds upon which copper is 
to be precipitated are upon the board. The surfaces of the moulds, 
as well as the heads of the pins, are then carefully rubbed with 
graphite, and the board is brought into the box filled with 
blue vitriol solution. The box B with the zinc plate is then sus- 
pended in the box A, and after filling it with dilute sulphuric acid, 
the two copper straps are connected by the binding screw E. The 
electric current then passes through the latter and the pin to the 
surface of the first matrice, and after depositing copper upon it 
passes through the second pin and the small copper plate to the 
second matrice, and so on, effecting a uniform deposit of copper 
upon all conducting surfaces connected with each other. 

Large ajiparatus. — To cover large surfaces, use large, square 
vats of stoneware, or of wood, lined with lead, gutta-percha, or 
another substance unacted upon by the bath. For baths up to 
three feet long stoneware vats are to be preferred. 

Fig. 120 shows the French form of cell apparatus. In the 
middle of the vat, and in the direction of its length, is disposed a 
row of cylindrical cells, close to each other, each provided with 
its zinc cylinder. A thin metallic ribbon is connected with all 
the binding screws of the cylinder, and is in contact at its extremi- 
20 



306 



ELECTRO-DEPOSITION OF METALS. 



ties with two metallic bands on the ledges of the depositing vat. 
The metallic rods supporting the moulds are in contact with the 



Fig. 120. 




metallic bands of the ledges, and, therefore, in connection with' 
the zincs. 




The German form of cell apparatus is shown in Fig. 121. It 
is provided with long, narrow, rectangular cells of a correspond- 
ingly greater height than the column of fluid. 



GALVANOPLASTY. 



307 



Across the vat are placed three conducting rods connected with 
each other by binding screws and copper wire. To the centre 
rod, which lies over the cells, are suspended the zinc plates by 
means of a hook, while the two outer rods serve for the reception 
of the moulds. 

The size of the zinc surfaces in the simple apparatus should be 
about equal to that of the surfaces to be moulded, if dilute sul- 
phuric acid (1.30) is to be used. For particulars see "Execution 
of the Galvanoplastic Deposition of Cooper." 

The copper bath for the cell apparatus consists best of a moder- 
ately saturated solution of pure blue vitriol, free from iron, in 
water free from lime, and should show about ]8° to 20° Be., a 
bath of 100 quarts requiring about 20 to 24 lbs. of blue vitriol.- 
The following table gives the approximate content of pure crys- 
tallized blue vitriol at different degrees Be., and 59° F. 









The solu 


tion contains 




Degrees, B6. 


Weight by volume. 


crystallized blue vitriol. 


5° 




1.035 


5 per cent. 


10° 










1.072 


11 


" 


12° 


, 








1.088 


13 


a 


15° 


. 








1.113 


17 


" 


16° 


. 








1.121 


18 


k 


17° 


, 








1.130 


19 


a 


18° 


. 








1.138 


20 


a 


19=5 










1.147 


21 


it 


20° 


. 








1.157 


23 


(< 


21° 










1.166 


24 


(< 


■ 22° 










1.176 


25 


a 



While to a copper bath working with the use of an external 
source of current more or less sulphuric acid is added, according 
to requirement, baths in the single cell apparatus do not require 
such addition, because a considerable quantity of the acid in the 
clay cell gradually penetrates by osmose into the bath ; and not 
only of the acid alone, but also of the white vitriol solution 
formed, whereby the working duration of the bath is considerably 
reduced. Furthermore, the sulphuric acid liberated by the sepa- 
ration of copper from the blue vitriol finds no saturation ; so that 
such a bath finally contains an excess of acid which for the pro- 
duction of good deposits must from time to time be removed, if 



308 ELECTRO-DEPOSITION OF METALS. 

it is not preferred to throw the bath away and make a fresh one. 
The simplest method of removing the excess of acid is to add to 
the bath pure carbonate of copper as long as strong effervescence 
takes place, blue vitriol being thereby formed, and hence the 
bath at the same time strengthened. Some operators remove the 
excess of acid by adding to the bath whiting free from iron, until 
no more effervescence takes place, and then filtering off from the 
calcium sulphate (gypsum) formed. The first-mentioned process 
is, however, preferable in every respect. 

2. Galvanoplastic Deposition by the Battery and Dynamo- 
Machine. 

Since it has been shown in the preceding section that a cell 
apparatus is to be considered as a Daniell element closed in itself, 
it will not be difficult to comprehend that in economical respects 
no advantage is offered by the production of galvanoplastic de- 
positions by a separate battery, because in both cases the chemical 
work is the same and the zinc dissolved by the use of the Daniell 
or Bunsen element effects no greater quantity of copper deposit in 
the bath than the same quantity of zinc dissolved in the cells of 
the single apparatus. In other respects the use of a battery, how- 
ever, offers great advantages. The employment of external 
sources of current requires the same arrangement as shown in 
Figs. 47 and 50, pp. 81 and 85 ; copper anodes being placed in 
the bath, which are connected with the anode pole of the battery. 

By this arrangement, while the copper is being deposited upon 
the mould, the copper anodes become dissolved by the sulphuric 
acid set free, forming sulphate of copper, which continued action 
keeps the copper content of the bath quite constant. Further- 
more, no foreign metallic admixtures reach the bath, as is the case 
in the single cell apparatus by the white vitriol solution penetrating 
from the clay cell into the bath and causing the formation of rough 
and brittle deposits of copper. The principal advantage, how- 
ever, is that by placing a resistance board in the circuit the cur- 
rent-strength can be controlled so that the deposits can be quickly 
covered with a strong current and then augmented with a weaker 
current, and that by intelligently regulating the current-strength, 



GALVANO PLASTY. 309 

deep depressions can also be covered, which is difficult in the 
single cell apparatus. 

A. Depositions with the Battery. 

The Daniell element described on p. 32, which yields a 
tension of about 1 volt, is much liked for this purpose. Since 
the copper bath for galvanoplastic purposes requires for its de- 
composition an electromotive force of only 0.5 to 1 volt, it will 
be best for slightly depressed moulds to couple the elements for 
quantity (Fig. 3, p. 18), alongside of each other; and only in cases 
where the particular kind of moulds requires a current of stronger 
tension, to couple two elements for tension one after the other, an 
excess of current being rendered innoxious by means of the resist- 
ance board or by suspending larger surfaces. 

Bunsen elements may, however, be used to great advantage, 
since the zincs of the Daniell elements become tarnished with 
copper and have to be frequently cleansed if the process is not to 
be retarded or entirely interrupted. The Bunsen elements need 
only be coupled for quantity, their electromotive power being con- 
siderably greater. To be sure, the running expenses are much 
greater than with Daniell elements, at least when nitric acid is 
used for filling. All that has been said under " Electro-plating 
arrangements in particular," page 76, in regard to conducting the 
current, the resistance boards, conducting rod, anodes, etc., is also 
valid for plants for the galvanoplastic deposition of copper with 
the battery. 

B. Depositions with Dynamo- Machines. 

It is best to use dynamos capable of yielding a large quantity 
of current with a tension of 2, or, at the utmost, 2| volts. In 
order to avoid repetition, the reader is referred to what has been 
said under "Arrangements with dynamo-electric machines," page 
93, the directions given there applying also to the galvanoplastic 
process. Since only in very rare cases the object-surface will be 
the same in all baths, it will be advisable to supply each of the 
baths, if several of them are worked with one dynamo-machine, 
with a resistance-board and a voltmeter. 



310 ELECTRO-DEPOSITION OF METALS. 

Copper baths for galvanoplastic depositions with a separate 
source of current. — The directions for the composition of the bath 
vary very much, some authors recommending a copper solution of 
18° Be. which is brought up to 22° Be. by the addition of pure 
concentrated sulphuric acid. Others again increase the specific 
gravity of the bath up to 25° Be. by the addition of sulphuric 
acid, while some prescribe an addition of 5 to 7 per ceut. of sul- 
phuric acid. It is difficult to give a general formula suitable for 
all cases, because the addition of sulphuric acid will vary accord- 
ing to the current-strength at disposal, the nature of the moulds, 
and the distance of the anodes from the objects. The object of 
adding sulphuric acid is, on the one hand, to render the bath 
more conductive and, when used in proper proportions, to make 
the deposit more elastic and smoother, and prevent the brittleness 
and coarse-grained structure which, under certain conditions, 
appear. When depositing with a battery somewhat more sul- 
phuric acid may be added to the bath than when employing the 
current of a dynamo-electric machine. The following composi- 
tions have, in most cases, been found suitable for the reproduction 
of shallow as well as of deep moulds. 

I. For depositing withihe dynamo. — Blue vitriol solution of 18° 
Be. 100 quarts, pure sulphuric acid of 6Q° Be. 1 to 1J quarts. 

II. For depositing with the battery. — Blue vitriol solution of 18° 
Be. 100 quarts, pure sulphuric acid of 6Q° Be. 1J to 2 quarts. 

For some special uses, the composition of the bath has to be 
somewhat modified, which will be referred to later on. In regard 
to the elasticity, strength, and hardness of galvanoplastic deposi- 
tions of copper, v. Hiibel found that copper of great toughness, but 
of less hardness and strength, is obtained with a current density 
of 0,6—1.0 ampere from an 18 per ceut. blue vitriol solution, and 
copper of great hardness and strength, but of little toughness, 
with 2 to 3 amperes, from a 20 per cent, solution. 

For copper printing -plates, a 20 per cent, solution, compounded 
with 3 per cent, of sulphuric acid, and a current- density of 1.3 
amperes, was found most suitable. 

Many operators prefer as a bath a solution of pure blue vitriol 
of 22° Be\, without any addition of sulphuric acid. A good 
deposit is obtained in such a bath, but a tension of 2 to 2J 



G A LVANOPL ASTY, 



311 



volts is required, while acidulated baths need only f to 1 J volts, 
according to the content of acid. 

Very fine deposits have also been obtained in baths consisting 
of a blue vitriol solution of 21° Be, brought up to 22° by the 
addition of sulphuric acid. This shows that it is not necessary 
to stick to a fixed unlimited composition of the baths, provided 
it is understood how to bring the current-condition into harmony 
with the composition. 

According to the composition of the bath, a fixed minimum 
and maximum current-density correspond to it, which must not 
be exceeded if useful deposits are to be obtained. There is, how- 
ever, a further difference according to whether the bath is at rest 
or in motion, v. Hiibl obtained the following results : — 





Composition of solution. 




Minimum and maximum curren 
per 15.5 square inches. 


-density 




With solution at 

rest. 

Amperes. 


With solution in 

gentle motion. 

AmpSres. 


15 per cent, blue 
plmric acid 


vitriol, 


without 


sul- 


2.6 to 3.9 


3.9 to 5.2 


15 per cent, blue 
cent, sulphuric 

20 per cent, blue 
pliuric acid 


vitriol 
acid 
vitriol, 


, with 6 
without 


per 

sul- 


1.5 " 2.3 
3.4 " 5.1 


2.3 " 

5.1 " 


3.0 

6.8 


20 per 
cent. 


cent, blue 
sulphuric 


vitriol 
acid 


, with 6 


per 


2.0 " 3.0 


3.0 " 


4.0 



Touching the addition of sulphuric acid, it was shown that no 
difference in the texture of the deposit is perceptible if the addi- 
tion of acid varies between 2 and 8 per cent. 

The preceding table shows that a copper bath in gentle motion 
can stand considerably higher current densities, and hence will 
work with correspondingly greater activity than a bath at rest. 
In the electrolytic refining of copper it was found that for the 
faultless deposition of copper the bath must be maintained 
entirely homogeneous in all its parts. When a copper bath is 
at rest and the depositing operation in progress, the upper layers 
of the bath become poorer in copper than the lower, while at the 
same time they contain more sulphuric acid. This difference in 
the composition of the upper and lower layers has the disadvantage 



ELECTRO-DEPOSITION OP METALS. 




that the portions dipping into 
the layers richer in copper be- 
come more thickly coppered 
than those in the upper layers. 
Baths which are constantly in 
gentle motion show less inclina- 
tion to the formation of knots 
and other rough excrescences, 
and hence the current-density 
may be greater than with solu- 
tions at rest resulting in the 
deposition being effected with 
greater rapidity. These experi- 
ences gathered in electro-metal- 
lurgical operations on a large 
scale, have been advantageously 
applied to galvauoplasty. The 
constant motion of the copper 
bath may be effected in various 
ways." Stirring by hand is fre- 
quently relied upon, but it is 
liable to be accidentally omitted, 
and being of necessity intermit- 
tent allows time for partial sepa- 
ration to occur between two 
consecutive stirrings. Mechani- 
cal agitation, which is more cer- 
tain in its effects, may be applied 
by working a small screw pro- 
peller slowly at one end of the 
bath, or by blowing air into the 
solution constantly through a 
tube passing to the bottom of 
the vat, by means of a fan- 
blower or other arrangement. 

Where many copper baths 
are in operation, the agitation 
of the bath may be effected as 



GALVA NOPLASTY. 3 1 3 

follows : The baths are arrauged in the form of steps ; near the 
bottom each bath is provided with a leaden outlet-pipe (Fig. 122), 
which terminates over the next bath over a distributing gutter, or 
as a perforated pipe, h. From the last bath the copper solution 
flows into a reservoir, E, from which it is forced by means of a 
hard-rubber pump, i, into the reservoir, A, placed at a higher 
level ; from A it again passes through the baths B, C, and _D. A 
leaden steam coil may, if necessary, be placed in A, to increase 
the temperature if it should have become too low. Over A a 
wooden frame covered with felt may be placed ; the copper solu- 
tion flowing upon the frame and passing through the felt is 
thereby filtered. 

Whatever motion is given to the bath it must be sufficiently 
vigorous to insure thorough mixture of the solution, but withont 
disturbing the relative positions of anode and cathode, and the 
mechanism must be so applied that it in no way lessens the facili- 
ties for examining the progress of deposition. 

Annealed sheets of pure copper are used as anodes ; impure 
anodes introduce other metallic constituents into the bath, which 
might result in a brittle deposit. It is recommended daily to free 
the anodes from adhering residues by brushing, so as to decrease 
the collection of slime in the bath. 

The anodes should present at least as large a surface as the 
cathodes; for flat moulds the distance between them and the 
anodes may be two to- three inches, but has to be increased for 
deeper moulds. The copper withdrawn from the bath by depo- 
sition being only partially replaced by the anodes, the content of 
free acid will increase in consequence of the reduction of the con- 
tent of copper. However, the copper wanting can be readily 
replaced by suspending bags filled with blue vitriol in the bath, 
while too large an excess of acid is removed by the addition of 
copper carbonate. 

Determination of free acid. — The free acid is determined by 
titrating the copper solution with normal soda solution, congo 
paper being used as an indicator. Bring by means of a pipette, 
10 cubic centimetres of the copper bath into a beaker glass, dilute 
with the same quantity of distilled water, and add drop by drop 
from a burette normal soda solution, stirring constantly, until 



314 ELECTRO-DEPOSITION OF METALS. 

congo paper is no longer colored bine, when moistened with a 
drop of the solution in the beaker glass. The cubic centimetres 
of normal soda solution consumed multiplied by 4.9 give the 
number of grammes of sulphuric acid in the liter. 

Suppose up to the appearance of the final. reaction by means of 
congo paper, which indicates that all the free sulphuric acid has 
been saturated by the normal soda solution, 11.99 cubic centi- 
metres of normal soda solution had been used for 10 cubic 
centimetres of copper bath, then one liter of the bath contains 
11.9x4.9 = 58.31 grammes of sulphuric acid. 

Determination of the content of copper according to Ham. — This 
method is based upon the conversion of blue vitriol and potassium 
iodide into copper iodide and free iodine. By determining the 
quantity of separated free iodine by titrating with solution of 
sodium hyposulphite of known content, the content of blue vitriol 
is found by simple calculation. The process is as follows : Bring 
10 cubic centimetres of the copper bath into a measuring flask 
holding jIq liter, neutralize the freed acid by the addition of 
dilute soda lye until a precipitate of bluish cupric hydrate, which 
does not disappear even with vigorous shaking, commences to 
separate. Now add, drop by drop, dilute sulphuric acid until 
the precipitate just dissolves; then fill the measuring flask up to 
the mark with distilled water, and mix by vigorous shaking. Of 
this solution bring 10 cubic centimetres by means of a pipette 
into a flask of 100 cubic centimetres' capacity and provided with 
a glass stopper; add 10 cubic centimetres of a 10 per cent, 
potassium iodide solution, dilute with some water, and allow the 
closed vessel to stand about 10 minutes. Now add from a burette, 
with constant stirring, a decinormal solution of sodium hyposul- 
phite until starch-paper is no longer colored blue by a drop of 
the solution in the flask. Since 1 cubic centimetre of decinormal 
solution corresponds to 0.0249 gramme of blue vitriol (==0.0063 
gramme of copper), the content of blue vitriol in one liter of the 
solution is found by multiplying the number of cubic centimetres 
of decinormal solution consumed by 24.9. For the correctness 
of the result it is necessary that the copper bath should be free 
from iron. 

Suppose 7.2 cubic centimetres of decinormal solution of sodium 



GALVANOPLASTY. 315 

hyposulphite have been used, the bath would contain 7.2 x 24.9 
= 179.28 grammes of blue vitriol. 

If now by these two determinations, the content of free acid 
and of blue vitriol in the bath has been ascertained, a comparison 
with the contents originally present in preparing the bath will 
show how many grammes per liter the content of acid has 
increased, and how many grammes the content of copper has 
decreased. Then by a simple calculation it is found how much 
dry pure carbonate of copper has to be added per liter of solution 
to restore the original composition. For each gramme more of 
sulphuric acid than originally present, 1.26 grammes of carbonate 
of copper have to be added, and each gramme of carbonate of 
copper increases the content of blue vitriol 2.02 grammes per liter 
of bath. By reference to these data the operator is enabled to 
calculate whether the quantity of carbonate of copper added for 
the neutralization of the excess of free acid suffices to restore the 
original content of blue vitriol ; or whether, and how much, blue 
vitriol per liter has to be added. 

Preparation of moulds (matrices) in plastic material. — If a nega- 
tive of the original for the production of copies is not to be made 
by direct deposition upon a metallic object, the negative has to be 
prepared by moulding the original in a plastic mass, which on 
hardening will retain the forms and lines of the design to the 
finest hatchings. Gutta-percha, wax (stearine, etc.), plaster of 
Paris, glue, and a few readily fusible metals are suitable materials 
for this purpose. 

Since the galvanoplastic process as far as it applies to electro- 
typing, will next be considered, we first direct our attention to the 
preparation of moulds or matrices of gutta-percha and wax, the 
only materials suitable for this purpose, and which are generally 
used. 

1. Moulding in gutta-percha. — For the reproduction of the 
fine lines of a wood-cut or copper-plate, pure gutta-percha freed 
by various cleansing processes from the woody fibres, earthy 
substances, etc., found in the crude product, is very suitable. 
Besides the requisite degree of purity, the gutta-percha should 
possess three other properties, viz., it must become highly plastic 



316 ELECTRO-DEPOSITION OP METALS. 

by beating, without, however, becoming sticky, and finally it 
should rapidly harden. 

The most simple way of softening gutta-percha is to place it in 
water of 176° to 194° F. When thoroughly softened no hard 
lumps should be felt in kneading with the hands, in doing which 
the latter should be kept thoroughly moistened with water. A 
fragment corresponding to the size of the object to be moulded is 
then rolled into a plate about ^ to f inch thick. To facilitate 
the detachment of the mould after cooling, the surfaces of the 
objects to be moulded, as well as the side of the gutta-percha 
which is to receive the impression, should be well brushed with 
black-lead (plumbago or graphite). The black-leaded surfaces 
are then placed one upon the other, and after gently pressing the 
gutta-percha with the hand upon the original the whole is placed 
in the press. To stop the further movement of the press-plate 
and prevent injury to the mould by too strong a pressure, small 
iron blocks, somewhat higher than the frame containing the object 
to be moulded and the gutta-percha plate are placed on both sides 
of the frame. The screw of the press is then made to act until 
the press-plate touches the iron blocks ; under this pressure the 
gutta-percha is allowed to cool and harden. 

For making the impression of the form in the moulding com- 
position, a moulding press is used which is capable of giving a 
gradual and powerful pressure. Fig. 123 represents a form of 
moulding press in common use, and known as the "toggle" 
press. It consists of a massive frame having a planed movable 
bed over which a head is swung on pivots and counter-balanced 
by a heavy-weight, as shown, so that it can be readily thrown up, 
leaving the bed exposed, the black-leaded type-form being placed 
on the bed. The well black-leaded case is attached by clamps to 
the movable head, or the form (also black-leaded) is laid face 
down on the case, and the head is then turned down and held in 
place by the swinging bar (shown turned back in the cut). All 
being ready, the toggle-pressure is put on by means of the hand- 
wheel and screw, the result being to raise the bed of the press 
with an enormous pressure, causing the face of the type-form to 
impress itself into the exposed moulding surface. 



GALVANOPLASTY. 



317 



Fig. 124 represents a form of " hydraulic press" less commonly- 
used than that just described. It is provided with projecting 




rails and sliding plate, on which the form and case are arranged 
before being placed in the press. The pump, which is worked 
by hand, is supported by a frame-work on the cistern below the 
cylinder, and is furnished with a graduated adjustable safety-valve 
to give any desired pressure. 

2. Moulding in wax (stearine). — Beeswax is a very useful ma- 
terial for preparing moulds, but, like stearine, it is according to 
the temperature now softer and now harder, which must be taken 
into consideration. In the cold, pure beeswax is quite brittle and 



318 



ELECTRO-DEPOSITION OF METALS. 



apt to become full of fissures in pressing. To decrease the brittle- 
ness certain additions are made to the wax, Urquart recommend- 




ing the following mixture, which is frequently used in England : 
Beeswax 85 parts by weight, Venice turpentine 13, black-lead 
finely pulverized 2. 

According to Volkmer, a good mixture is obtained by melting 
together 70 parts of wax and 30 of stearine. Watt prefers a 
mixture consisting of 70 parts of wax, 26 of stearine, and 4 of 
litharge or flake-white. G. L. v. Kress recommends the follow- 
ing mixture : "White wax 42.32 ozs., stearine 14.11 to 21.16 ozs., 
tallow 1058 ozs., graphite 1.76 ozs. First melt the asphalt over 
a moderate fire, then add the wax, stearine, and tallow, and when 
these are melted, the graphite ; stir until the mixture begins to 
congeal. 

To prepare the wax mould pour the melted composition into 
flat metallic trays provided with loops for suspension in the bath. 
When the composition is nearly set remove any bubbles of air or 



GALVANOPLASTY. 319 

impurities from the surface with blotting-paper. After black- 
leading the surface press the original, also black-leaded, upon the 
composition and submit the whole to pressure until cold. When 
the black-leading has been carefully done there is no difficulty in 
detaching the original after cooling ; many operators slightly oil 
the surface of the original instead of black-leading:. 

When the mould of gutta-percha or wax has been properly 
made, it is thoroughly black-leaded in order to give it a conduct- 
ing surface upon which the electro-deposition of the copper may 
take place. Black-leading must be very thorough so that the 
black-lead penetrates into every line and letter of the mould, 
otherwise the copper deposited on the surface will be an imperfect 
copy of the original, and it will be useless to place the mould in 
the bath. The black-lead used in every stage of the electrotyping 
process must be of the purest description and in the most minute 
state of division. The best material for the purpose is prepared 
from the purest selected Ceylon graphite, which is ground by 
rolling with heavy iron balls until it is reduced to a dead-black, 
impalpable powder. 

Black-leading the moulds is performed either by hand or more 
commonly by machines. 

Fig. 125 shows one of these machines with its cover removed 
to exhibit its construction. It has a travelling carriage holding 
one or more forms, which passes backward and forward, under 
a laterally vibrating brush. Beneath the machine is placed an 
apron which catches the powder, which is again used. 

Another construction of a black-leading machine is shown in 
Fig. 126, the details of which will be understood without lengthy 
description. The moulds are placed upon the slowly revolving, 
horizontal wheel upon which the brush moves rapidly up and 
down with a vertical, and at the same time laterally, vibrating 
motion. The black-leading space being closed air-tight, scatter- 
ing of black-lead dust is entirely prevented, the excess of black- 
lead collecting in a vessel placed in the pedestal. 

On account of the dirt and dust caused by the dry process of 
black-leading, some electrotypers prefer the wet process invented 
by Mr. Silas P. Knight, of New York. This process is designed 
to work more quickly and neatly, producing moulds that are 



320 



ELECTKO-DEPOSITION OF METALS. 



thinly, evenly, and perfectly covered. The moulds are placed 
upon a shelf in a suitable receptacle, and a rotary pump forces an 

Fig. 125. 




emulsion of graphite and water over their surfaces through a 
travelling fine-rose nozzle. This process is pronounced to be 
rapid, efficient, neat, and economical. 

With very deep forms of type, it is sometimes of advantage to 
first coat the black-leaded surface with copper, in order to obtain 
a uniform deposit in the bath. The process is as follows : Pour 
alcohol over the black-leaded form, let it run off and then place 
the form horizontally over a water trough. Now pour over the 
form blue vitriol solution of 15° to 16° Be., dust upon it from a 
pepper-box some impalpably fine iron filings and brush the mix- 
ture over the whole surface, which thus becomes coated with a 



G A LVANOPLASTY. 



321 



thin, bright, adherent film of copper. Should any portion of the 
surface after such treatment remain uncoppered, the operation is 



Fiff. 126. 




repeated. The excess of copper is washed off and the form, after 
being provided with the necessary conducting wires, is ready for 
the bath. 

Gilt or silvered black-lead is also sometimes used for very 
deep forms. It is, however, cheaper to mix the black-lead with 
■| its weight of finest white bronze powder from finely divided 
tin. When forms thus black-leaded are brought into the copper 
bath, the particles of tin become coated with copper, also causing 
a deposit upon the black-lead particles in contact with them. 

After black -leading the workman takes one or several stout 
copper wires, the ends of which, after thorough cleansing, he 
heats for an instant, and imbeds them in the wax on the side of 
the mould. The surface of this wire is carefully exposed, and by 
way of precaution the place is rubbed with black-lead with the 
finger to restore the black-lead surface that may have been dis- 
turbed. Trifling as this circumstance of exposing the imbedded 
21 



322 ELECTRO-DEPOSITION OF METALS. 

wire may appear, the galvanic deposit of the copper on the face 
of the mould would be impossible were it neglected, as the mass 
of wax being a non-conductor of electricity, a galvanic current 
could not otherwise be established. The exposure of the wire, 
therefore, is essential in order that the surface of the mould may 
be rendered properly conductive to insure the uniform deposition 
of copper upon it. To confine the deposit of copper where it is 
actually desired, and to prevent it from unnecessarily spreading 
over the edges of the mould, a tool called the " building iron" is 
heated and run over the mould so as to destroy the continuity of 
the black-lead surface, save where the deposit of copper is 
wanted. 

In order that the deposition of copper may be as nearly uniform 
in thickness as possible over the entire surface of the mould, it 
becomes necessary, where a large surface is to be coated, to pro- 
vide as much metallic surface as possible on which the deposit of 
copper may commence and spread. One method of accomplish- 
ing this, is to attach one or more pieces of metal to the wax on 
the edges of the mould, and connect them with the slinging wires 
by good metallic connections. 

A very practical device in this connection is the "electric-con- 
nection gripper" of Messrs. R. Hoe & Co., of New York. This 
arrangement is designed to hold and sustain the moulding case, 
and at the same time to make an electric connection with the pre- 
pared conducting face of the mould only ; consequently, leaving 
the metal case itself entirely out of the current, so that no copper 
can be deposited on it. 

Gutta-percha being specifically lighter than water, moulds of 
this material have to be provided with a piece of heated lead 
stuck to the back to prevent them from floating, and to force 
them to occupy a perpendicular position opposite to the anodes. 

The moulds are suspended in the bath in the same manner as 
in other galvanic processes, special care being had that their sur- 
faces hang parallel to the anodes, so that all portions may receive 
a uniform deposit. Before placing the mould in the bath, pour 
over it, while in a horizontal position, a mixture of equal parts 
of alcohol and water ; by this means, a uniform moistening of the 



GALVANOPLASTY. 323 

mould in the bath is attained, and the settlement of air-bubbles 
on it prevented. 

For the production of a dense, coherent, and elastic deposit in 
the acid-copper bath, the chief requisite is to have the current- 
strength in the correct proportion to the surface to be coated, this 
applying to deposition with the single-cell apparatus, as well as 
with an external source of current. 

The stronger the sulphuric acid in the clay cells of the simple 
apparatus is, with the greater rapidity it acts upon the zinc plates, 
and the more quickly is the copper deposited upon the moulds. 
If the zinc surface of the clay cells is very large in proportion to 
the surface of the moulds, the deposition of copper also takes 
place with correspondingly greater rapidity. However, a rapid 
deposition of copper is to be avoided, if deposits possessing the 
above-mentioned desirable properties are to be obtained, because 
a deposit forced too much, turns out incoherent, lacking in density, 
is frequently blistered, and, with too strong action, is even 
pulverulent. The color of the deposit furnishes a certain criterion 
for its quality ; a red-brown color indicating an unsuitable de- 
posit, and a beautiful rose color a good serviceable one. 

One part of concentrated sulphuric acid of 66° Be. to 30 of 
water has formerly been given as the proper proportions for the 
dilute acid used for filling the clay cells, provided the zinc sur- 
face be about the same as that of the moulds. If the zinc sur- 
face is smaller than that of the moulds, stronger acid may be 
used; but if it is larger, the acid will have to be more dilute. 
The correct concentration of the acid in the clay cells may be 
readily determined by the progressive result of the deposit and 
its color. Deep moulds .require a stronger current, and hence 
acid of greater strength than flat moulds ; however, if after such 
deep moulds are provided with a preliminary deposit, the current 
proves too strong for the correct progress of the operation, its 
action may be weakened by either diluting the acid in the clay 
cells with water, or by taking out a few zinc plates, or by hang- 
ing a few copper sheets upon the object-rods, or suspending more 
moulds. 

For the deposition of copper with a separate source of current 
(battery or dynamo), the same that has been said above applies as 



324 ELECTRO-DEPOSITION OF METALS. 

regards the current-strength, which must be brought to a suitable 
degree by the resistance board. The most suitable current- 
density for the production of a good deposit is 1.5 to 2 amperes 
per 15 \ square inches of surface of moulds for baths for depo- 
sitions with a separate source of current, given on page 310, if at 
rest, and 2 to 3 amperes if in motion. 

Since even for deeper moulds a tension of 1.5 volts suffices, if 
the bath is acidulated, the more powerful Bunsen elements will 
have to be coupled alongside one another; but two of the weaker 
Daniell or Lallande elements one after the other, and of such 
groups, as many as are required, will have to be coupled along- 
side one another for quantity of current (see page 18), to make 
the active zinc surface nearly equal to that of the moulds. How- 
ever, for flat moulds coupling the separate weaker elements along- 
side one another is also sufficient. When the moulds are coated 
with copper on every side, and also the deeper portions, the cur- 
rent is weakened if a copper deposit of pulverulent or coarse- 
grained structure and of a dark color should appear on the edges 
of the moulds, and it is feared that the deposit upon the design 
or type might also turn out pulverulent. The current, however, 
should only be sufficiently weakened to prevent a further pro- 
gress of the dark deposit on the edges towards the interior of the 
surface of the mould. If, however, by too strong a current the 
separation of a pulverulent deposit upon the design has already 
taken place, the deposit may generally be saved, if the fact is 
noticed in time, and the current correspondingly weakened, as the 
layers are firmly united by the coherent copper then deposited. 

The current of the dynamo-machine must also be sufficiently 
weakened by the resistance board in front of the bath, or by that 
of the machine to guarantee the good quality of the deposit. For 
deeper moulds the tension for covering may amount to 1 or 1.5 
volts, and for very deep and steep moulds to 1.5 or 2 volts. But 
when the moulds are completely covered the current is reduced to 
about 0.75 volt,* aud the operation finished with this tension. 

The average time required for the production of a sufficiently 
heavy deposit with a dynamo-machine is from 7 to 8 hours. In 

* These current-strengths refer to formulae I. and II. given on page 310. 



GALVANOPLASTY. 325 

this time the deposit acquires a thickness of about ^ millimetre 
(0.013 iuch), which corresponds to a weight of about 25 grammes 
(14.11 drachms) of copper per 15J square inches. 

Xow, since it frequently happens that an electrotype has to be 
finished and delivered in a hurry, the work may have to be con- 
tinued during the night; but as it may not be desirable to have 
the dynamo running, either a cell apparatus or accumulators have 
to be employed. In using a cell apparatus, it is advisable to first 
quickly coat the moulds by the current of the dynamo, and then 
finish the deposit in the apparatus. 

In modern times accumulators have been successfully used for 
the same purpose. 

A detailed description of the accumulators and directions for 
their treatment may here be omitted, they being furnished by the 
manufacturers of the various systems. Each accumulator con- 
sists of a number of alternately positive and negative lead plates 
immersed in a vessel filled with dilute sulphuric acid. By con- 
ducting the current of a dynamo-machine into the accumulator 
so that the positive current passes into the positive plates, and the 
negative current into the negative plates, lead peroxide is formed 
upon and in the porous positive plates by the co-operation of the 
sulphuric acid and the oxygen appearing on the positive pole, and 
the greater the quantity of lead peroxide thus formed, the more 
electricity is stored in the accumulators. These operations are 
called charging the accumulator. By interrupting the introduc- 
tion of a current and closing the circuit of the positive and nega- 
tive plate systems by the introduction of electrodes in an electro- 
lyte (galvanic bath), a current is developed whereby the lead 
peroxide of the positive plates which has been formed is reduced 
to lead, while the negative plates are oxidized to lead peroxide. 
This process is termed discharging. The chemical processes ap- 
pearing thereby are of more complicated nature than here given, 
but are omitted so as to render comprehension of the process 
less difficult. The directions for charging and discharging the 
accumulator must be strictly followed, and require great atten- 
tion, as charging with too strong a current, or a too abundant 
discharge may cause the rapid destruction of the plates. The 



326 ELECTRO-DEPOSITION OF METALS. 

charging is best done during the day with a special small dynamo- 
machine. 

Detaching the deposit from the mould. — When the mould has 
received a suitable deposit, it is taken from the bath, rinsed in 
water, and all edges which might obstruct the detachment of the 
deposit from the mould are removed with a knife. From gutta- 
percha moulds the deposit is gradually lifted by inserting under 
one corner a flat horn plate or a thin dull brass blade and apply- 
ing a very moderate pressure ; particles of gutta-percha which 
may remain adhering are carefully burnt off over a flame. Wax 
moulds are placed in an inclined position, and a stream of hot 
water is poured over the copper surface, by which means the wax 
is sufficiently softened to allow the shell of copper to be stripped 
off. This may be done by taking hold of one corner of the shell 
and quickly lifting it as the hot water flows over it. In removing 
the shell care should be taken to keep it straight, as otherwise it 
will be difficult to back and finish it properly. 

Baching the deposit or shell. — The tinning of the back of the 
shell is the next operation, and has for its object to strengthen the 
union between the shell and the backing metal. For this purpose 
the back of the shell is cleansed by brushing with "soldering-fluid," 
made by allowing muriatic acid to take up as much zinc as it will 
dissolve, and diluting with about J of water, to which some sal 
ammoniac is sometimes added. Then the shell, face down, is 
heated by laying it upon an iron soldering plate, floated on a bath 
of melted stereotype metal, and, when hot enough, melted solder 
(half lead and half tin) is poured over the back, which gives it 
a clean, bright metallic covering. Or, the shell is placed down- 
ward in the backing-pan, brushed over the back with the solder- 
ing fluid, alloyed tinfoil spread over it, and the pan floated on the 
hot backing metal until the foil melts and completely covers the 
shell. When the foil is melted the backing pan is swung on to a 
levelling stand, and the melted backing metal is carefully poured 
on the back of the shell from an iron ladle, commencing- at one 
of the corners and gradually running over the surface until it is 
covered with a backing of sufficient thickness. Another method 
is as follows : After tinning the shell it is allowed to take the 



GALVANOPLASTY. 



327 



temperature of the backing metal on the floating iron plate. The 
plate is then removed from the melted metal, supported in a level 
position on a table having projecting iron pins on which it is 
rested, and the melted stereotype metal is carefully ladled to the 
proper thickness on the back of the tinned shell. This process is 
called "backing." The thickness of the metal-backing is about 
an eighth of an inch. A good composition for backing metal 
consists of lead 90 parts, tin 5, and antimony 5. 

Finishing. — For this purpose the plates go first to the saw table 
(Fig. 127), for the removal of the rough edges by means of a 

Fig. 127. 




circular saw. The plates are then shaved to take off any rough- 
ness from the back and make them of even thickness. In large 
establishments this portion of the work, which is very laborious, 
is done with a power planing or shaving machine, types of which 
are shown in Figs. 128 and 129, Fig. 128 being a shaving machine 



328 



ELECTRO-DEPOSITION OF METALS. 



with steam one way, and Fig. 129 one with steam both ways. 
The flatness of the plates is then tested with a straight edge and 



Fig. 128. 




any unevenness rectified by gentle blows with a polished hammer, 
taking every care that the face be not damaged. The plate then 
passes to the hand shaving machine, where the back is shaved 
down to the proper thickness, smooth and level. The edges of 
the plate are then planed down square and to a proper size, and 
finally the plates are mounted on wood type-high. Book-work 
is generally not mounted on wood, the plates being left un- 
mounted and finished with bevelled edges, by which they are 
secured on suitable plate-blocks of wood or iron supplied with 
gripping pieces, which hold them firmly at the proper height and 
enable them to be properly locked up. 



GALVANOPLASTY. 



329 



Finally, it remains to say a few words about the process by 
which a copy may be directly made from a metallic surface with- 



Fig. 129. 




out the interposition of wax or gutta-percha. If the metallic 
surface to be moulded were free from grease and oxide, the deposit 
would adhere so firmly as to render its separation without injury 
almost impossible. Hence, the metallic original must first un- 
dergo special preparation, so as to bring it into a condition favor- 
able to the detachment of the deposit. This is done by thoroughly 
rubbing the original with an oily rag, or, still better, by lightly 
silvering it and exposing the silvering for a few minutes to an 
atmosphere of sulphuretted hydrogen, whereby sulphide of silver 
is formed, which is a good conductor, but prevents the adherence 
of the deposit to the original. For the purpose of silvering, free 
the surface of the metallic original (of brass, copper, or bronze) 
from grease, and pickle it by washing with dilute potassium 
cyanide solution (1 part potassium cyanide to 20 water). Then 
brush it over with a solution of 4^ drachms of nitrate of silver 



330 ELECTRO-DEPOSITION OF METALS. 

and 1 oz. 6 drachms of potassium cyanide (98 per cent.) in 1 
quart of water; or, still better, immerse the original for a few 
seconds in this bath, until the surface is uniformly coated with 
a film of silver. The production of the layer of sulphide of 
silver is effected according to the process described later on 
(p. 338). The negative thus obtained is also silvered, made 
yellow with sulphuretted hydrogen, and a deposit of copper is 
then made, which represents an exact copy of the original. In- 
stead of sulphurizing the silvering with sulphuretted hydrogen 
it may also be iodized by washing with dilute solution of iodine 
in alcohol. The washed plate, prior to bringing it into the copper 
bath, is for some time exposed to the light. 

To prevent the separation of copper on the back of the metallic 
original to be copied, it is coated with asphalt lacquer, which 
must be thoroughly dry before bringing into the bath. When 
the deposit of copper is of sufficient thickness, the plate is taken 
from the bath, rinsed in water, and dried. The edges are then 
trimmed off by filing or cutting to facilitate the separation of the 
shell from the original. 

Of course, only metals which are not attacked by the acid 
copper solution can be directly brought into the bath. Steel 
plates must therefore first be thickly coppered in the alkaline 
copper bath (p. 194), and even this precaution does not always 
protect the plate from corrosion. It is therefore better to produce 
in a silver bath (formula I., p. 213) a copy in silver of sufficient 
thickness to allow of the separation of both plates. The silver 
plate is iodized, and from it a copy in copper is made by the gal- 
vanoplastic process. The copper plate thus obtained is an exact 
copy of the original, and after previous silvering the desired 
number of copies may be made from it. 

Electro-etching. — The lines produced by the ordinary process 
of etching actually represent, when viewed under the microscope, 
a continuous series of irregular depressions and small cavities, and 
when some depth is required they are apt to be corroded under- 
neath, and to increase so much in width that the plates are fre- 
quently spoiled. None of these objections applies to the galvanic 
process of etching, which is the invention of Thomas Spencer. 
Each line, when viewed under the microscope, represents a perfect 



GALVANOPLASTY. 331 

furrow, and is just rough enough — for instance, in the prepara- 
tion of printing plates — to hold the printing ink. Lines of con- 
siderable depth may be produced without the danger of extending 
in width or corroding underneath. The corners of the intersec- 
tion of two lines are as sharp as if the lines were engraved. A 
chief requisite for electro-etching is a good etching ground, since 
it may frequently happen that the latter may answer very well for 
the ordinary process, but is not capable of offering sufficient resist- 
ance to the electric current. A great advantage in electro-etching 
is that the solvent is always of the same strength, and, therefore, 
constant in its action, and that there is no evolution of acid vapors 
which are injurious to the respiratory organs. 

The operation of electro-etching is conducted as follows : A 
conducting wire is soldered with tin solder to the object, and the 
latter is then coated with the etching ground. The design is then 
traced with a graver, taking care that the tool lays bare the metal 
in all the lines. The object thus prepared is connected with the 
positive pole and suspended in the bath, while a plate of the same 
metal as the object is secured to the negative pole. The bath con- 
sists of a dilute acid corresponding to the metal of the object. For 
silver dilute nitric acid is used ; for gold and platinum, water 
acidulated with aqua regia; for copper, brass, and zinc, water 
acidulated with sulphuric acid ; and for tin, water acidulated with 
hydrochloric acid. Baths containing the metal to be etched in 
solution, however, work better than acids diluted with water. 
Thus, for gold and platinum, chloride of gold and platinic chloride 
are used; for silver, solution of nitrate of silver; for copper and 
brass, solution of blue vitriol ; for iron and steel, solution of 
green vitriol, or of ammonium chloride, or a combination of both ; 
for zinc, solution of white vitriol or of chloride of zinc, etc. There 
are besides various metallic salts suitable for etching by them- 
selves or in combination with the above-named salts. 

As etching ground various compositions may be employed, it 
being, however, best to use, if possible, one which can be readily 
removed. A mixture of equal parts of asphalt and copal varnish 
forms a good etching ground ; also a composition obtained by 
melting together asphalt 2| parts, wax 2, rosin 1, and black pitch, 
2. How T ever, the following composition, which resists 25 per 



332 ELECTRO-DEPOSITION OF METALS. 

cent, nitric acid, is to be preferred. It is prepared as follows: 
Melt yellow wax 4 parts, Syrian asphalt 4, black pitch 1, and 
white Burgundy pitch 1. When the mixture boils gradually add, 
with constant stirring, 4 parts more of pulverized Syrian asphalt. 
Continue boiling until a sample poured upon a stone and allowed 
to cool breaks in bending. Then pour the mixture into cold 
water and shape it into small balls, which for use are dissolved in 
oil of turpentine. 

Since the current-strength is under perfect control, the etching 
may be carried to any depth desired. Some portions may be less 
etched than others by taking the plate from the bath, and, after 
washing and drying, coating the portions which are not to be 
further etched with lacquer, and returning the plate to the bath. 

Printing plates in relief may in this manner be prepared by 
slightly etching the bared design of a copper-plate in the gal- 
vanoplastic copper bath, and then bringing the plate as object in 
contact with the negative pole, while a plate of chemically pure 
copper serves as anode. The deposited copper unites firmly with 
the rough copper of the etched plates, and after removing the 
etching-ground with benzine or oil of turpentine the design 
appears in relief. 

Heliograjjhy . — By this term are understood several methods of 
printing, in which plates of asphalt, chrome-gelatine, etc., pro- 
duced by exposure to light, are used. For our purposes only 
the method is of interest by which from the negative, produced 
by the action of light, a galvanoplastic reproduction — printing 
plates in high and low relief — in metal is made. The heliographic 
process invented by Pretsch and improved by Scamoni, consists 
in taking by photography a good negative of the engraving or 
other object to be reproduced, developing with green vitriol, rein- 
forcing with pyrogallic acid and silver solution, and then fixing 
with sodium hyposulphite solution in the same manner as custo- 
mary for photographic negatives. A further reinforcement with 
chloride of mercury solution then takes place until the layer ap- 
pears light gray. Now wash thoroughly and intensely blacken 
the light portions by pouring upon them dilute potassium cyanide 
solution. As in the photographic process, the solutions must be 
applied in abundance and without stopping, as otherwise streaks 



GALVANOPLASTY. 333 

and stains are formed. After washing, the plate is dried, further 
reinforced, and finally coated with colorless negative varnish. 
From this negative a positive collodion picture is taken, which 
is in the same manner developed, reinforced, and fixed, the rein- 
forcement with pyrogallic acid being continued until the picture 
is quite perceptibly raised. After careful washing, pour upon the 
plate quite concentrated chloride of mercury solution, which has 
to be frequently renewed, until the picture, at first deep black, 
acquires a nearly white color, and the lines are perceptibly 
strengthened. Now wash with distilled water, next with dilute 
potassium iodide solution, and finally with ammoniacal water, 
whereby 'the picture acquires first a greenish, then a brown, and 
finally a violet-brown color. After draining, the plate may pro- 
gressively be treated with solutions of platinum chloride, gold 
chloride, green vitriol, and pyrogallic acid, the latter exerting a 
solidifying effect upon the pulverulent metallic deposits. The 
metallic relief is now ready ; the layer is slowly dried over alcohol, 
and the plate, when nearly cold, quickly coated with a thin rosin 
varnish, which, after momentary drying, remains sufficiently 
sticky to retain a thin layer of black lead, which is applied with 
a tuft of cotton. The edge of the plate is finally surrounded with 
wax, and, after being wired, the plate is brought into the galvano- 
plastic copper bath to be reproduced. 

Galvanoplastic reproduction of busts, vases, etc. — For this pur- 
pose an entirely different process of preparing the moulds than that 
described for electrotyping is required, the material for moulding 
depending on the nature of the original. Besides gutta-percha 
•and wax, readily fusible metals, plaster of Paris, and glue will 
have to be considered. If the original bears heating to about 
230° F., a copy in one of the readily fusible alloys given later 
on may be made; if it will stand heat and pressure, it is best to 
mould in gutta-percha ; but if neither heat nor pressure can be 
applied, the moulds will have to be executed in plaster of Paris 
or in glue. The manner of moulding and the material to be 
chosen furthermore depend on whether surfaces in high relief or 
round plastic bodies are to be copied, whether projecting portions 
are undercut, and whether the mould can be directly detached, or, 



334 ELECTRO-DEPOSITION OF METALS. 

if this is Dot the case, whether the original has to be dissected 
and moulded in separate parts. 

Regarding the practice of moulding, the reader is referred to 
special works on that subject ; only the main points for the most 
frequently occurring reproductions will here be given. 

Surfaces in relief and not undercut are readily moulded in an 
elastic mass such as gutta-percha or wax ; however, undercut 
reliefs and especially round plastic objects mostly require a plaster- 
of-Paris mould and are generally dissected ; the dissection being 
of course not carried further than absolutely necessary, because 
the separate parts must be united by a soldering seam which 
requires careful work, and the seam itself must be worked over 
and made invisible. Hence the section should as much as possible 
be made through smooth surfaces, edges, etc., where the subse- 
quent union by a soldering seam will prove least troublesome, 
while cutting through ornaments or through portions, the accurate 
reproduction of which is of the utmost importance, should be 
avoided. Heads and busts are always executed in a core mould 
and in portions unless the entire figure is to be deposited in one 
piece in a closed mould. The section is made either through the 
centre line of the head through the nose, which, however, makes 
the subsequent union very troublesome, if the copy is to be an 
exact reproduction of the original, or the mould is divided from 
ear to ear, which has the disadvantage that the deepest part of 
the mould corresponding to the nose receives the thinnest deposit. 
It has, therefore, been proposed to make two cuts so that three 
portions are formed ; one cut from one ear at the commencement 
of the growth of hair to the other ear ; and the second cut from ' 
one ear in a downward direction below the lower jaw in the joint 
of the head and neck, through this joint below the chin, and then 
upwards to the other ear, and in front of it to where the hair 
begins. In bearded male heads the cut follows the contour of the 
beard and not the joint on the neck behind the beard. 

To mould round articles in gutta-percha, the softened gutta- 
percha is kneaded with wet hands upon the oiled original, or, in 
order to avoid that some portions receive a stronger pressure than 
others, and to insure a layer of gutta-percha of uniform thickness 
upon all portions, the moulding may also be executed in a ring 



GALVANOPLASTY. 335 

or frame of iron or zinc under a press. For the rest, all that has 
been said in regard to moulding in gutta-percha on p. 315 is also 
applicable. 

The following metallic alloys have been proposed for the prepa- 
ration of moulds : — 

I. Lead 2 parts, tin 3, bismuth 5 ; fusible at 212° F. 
II. Lead 5, tin 3, bismuth 8 ; fusible at 185° F. 

III. Lead 2, tin 2, bismuth 5, mercury 1 ; fusible at 158° F. 

IV. Lead 5, tin 3, bismuth 5, mercury 2 ; fusible at 127.5° F. 
The advantage of metallic moulds consists in that the metal is 

a good conductor of electricity, in consequence of which heavy 
deposits of greater uniformity can be produced than with non- 
metallic moulds which have been made conductive by black lead. 
Nevertheless, they are but seldom employed on account of the 
crystalline structure of the alloys and the difficulty of avoiding 
the presence of air bubbles. Bo'ttger claims that a mixture of 
lead 8 parts, tin 3, and bismuth 8, which is fusible at 227° F., 
shows a less coarse-grained structure. 

Fusible alloys containing mercury should not be used for taking 
casts of metallic objects — iron excepted — as these will amalga- 
mate with the mercury and be injured. Moreover, copper de- 
posits obtained upon such alloys are very brittle, which is due to 
the combination of the mercury with the deposited copper. 

For moulding with metallic alloys place the oiled object at the 
bottom of a flat vessel and pour the liquid metal upon it ; or 
pour the liquid metal into a box, remove the layer of oxide with 
a piece of stout paper, and when the metal is just beginning to 
congeal firmly press the object in it. 

Plaster of Paris is used for making casts of portions from 
originals which are so strongly undercut that a mould consisting 
of one piece could not be well detached from them. For taking 
casts from metallic coins aud medals or from small plaster reliefs, 
it is a very convenient material. The mode of procedure is as 
follows : After the original model, say a medal, has been thoroughly 
soaped or black-leaded, wrap round the rim a piece of sufficiently 
stout paper or thin lead foil, aud bind it in such a manner by 
means of sealing-wax that the face of the medal is at the bottom 
of the receptacle thus formed. Then place the whole to a certain 



336 ELECTRO -DEPOSITION OF METALS. 

depth in a layer of fine sand, which prevents the escape of the 
semi-fluid plaster of Paris between the rim of the medal and the 
paper. Now mix plaster of Paris with water to a thin paste, 
take up a small quantity of this paste with a pencil or brush and 
spread it in a thin film carefully and smoothly over the face of 
the medal, then pour on the remainder of the paste up to a proper 
height and allow it to set. After a few minutes the plaster heats 
and solidifies. Then remove the surrounding paper, scrape off 
with a knife what has run between the paper and the rim of the 
medal, and carefully separate the plaster cast from the model. If 
instead of applying the first layer with a brush, the whole of the 
plaster were run at once into the receptacle, there would be great 
risk of imprisoning air bubbles between the model and the mould, 
which would consequently be worthless. The mould is finally 
made impervious and conductive according to one of the methods 
to be described later on. 

The moulding in plaster of Paris in portions, when casts from 
large plastic objects with undercut surfaces and reliefs are to be 
taken, is troublesome work, because each separate mould must not 
only be so that it can be readily separated without injury to the 
original, but must also fit closely to its neighbors. Hence thought 
and judgment are required to see of which parts separate moulds 
are to be made, or, in other words, in how many parts the mould 
is to be made. After determining on the plan of the work, the 
mode of procedure is as follows : Oil a portion of the object, if it 
consists of metal, or soap it, if of plaster of Paris, marble, wood, 
etc., and apply by means of a brush a thinly-fluid paste of plaster 
of Paris, taking care that no air bubbles are formed by the strokes 
of the brush. When this thin coat is hard, continue the applica- 
tion of plaster of Paris with a horn spatula until the coat has 
acquired a thickness of f to 1 inch, and allow it to harden. Then 
separate the mould, and after cutting or sawing the edges square 
and smooth, replace it upon the portion of the original model 
corresponding to it. Now oil or soap the neighboring portions of 
the model, and at the same time the smooth edges of the first 
mould which come in contact with the mould now to be made, 
and then proceed to make the second mould in precisely the same 
manner as the first. When the second mould is hard, trim the 



GAT.VAXOPLASTY. 337 

edges and replace it upon the model ; the same process being con- 
tinued until the entire original model is reproduced in moulds 
well fitting together. To prevent the finished moulds from fall- 
ing off, and to retain them in a firm position upon the original 
model, they are tied with lead wire or secured with catches of 
brass wire or sheet. When the moulds of the larger portion of 
the model, for instance, one-half of a statue, are finished, the 
so-called case or shell is made, i. e., the backs of all the moulds are 
coated with a layer of plaster of Paris which holds them together. 
This case is best made not too thin in order to attain a better resist- 
ing power. 

The entire model having been cast in the manner above 
described, and the moulds provided with the case, the whole is 
completely dried in an oven. 

The next operation is to make the plaster of Paris impervious 
to fluids, as otherwise, by the moulds absorbing the acid copper 
bath, copper would be deposited in the pores of the plaster and 
the moulds be spoiled, while the copy would turn out rough instead 
of having the smooth exterior of the model. To render plaster 
of Paris and other porous substances impervious, they are satu- 
rated with wax or stearine or covered with a coat of varnish, the 
latter process being generally employed for large moulds. Apply 
a coat of thick linseed oil varnish to the face of the mould, and, 
after drying, repeat the process until the mould is thought to be 
sufficiently impervious. Rendering the mould impervious with 
wax or stearine is a better and more complete method. For this 
purpose cut a groove in the rim of the mould, place in the groove a 
brass wire and twist the ends, which must be long enough to hold 
the mould by. The mould, having been previously dried, is then 
dipped into a bath of wax or stearine kept at a temperature of 
from 180° to 212° F., and a number of air bubbles will escape 
from the mould to the surface. When the production of air 
bubbles is considerably diminished, remove the mould from the 
bath, and lay it face up in a drying oven, whereby the melting 
wax in consequence of its gravity oozes down, and the face of the 
mould is freed from an excess of wax. Whenever possible, sub- 
merging the entire mould should be avoided and the operation be 
conducted as follows : Place the heated mould in a vat filled with 
22 



338 ELECTRO-DEPOSITION OF METALS. 

melted wax or stearine, so that the face does not come in contact 
with the wax, but absorbs wax by capillarity from the back. 

The moulds thus coated with varnish or saturated with wax 
are now made conductive with black-lead, the operation being the 
same as that mentioned on p. 319. For many undercut or deep 
portions black-leading is, however, not sufficient, and recourse 
must be had to making the moulds conductive or metallizing them 
by the wet way. 

Metallization by the. wet way. — This method consists in the 
deposition of certain metallic salts upon the moulds and their 
reduction to metal or conversion to conductive sulphur combi- 
nations. The process in general use is as follows : Apply with 
a brush upon the mould a not too concentrated solution of nitrate 
of silver in a mixture of equal parts of distilled water and 90 
per cent, alcohol. When the coat is dry expose it in a closed box 
to an atmosphere of sulphuretted hydrogen ; the latter converts the 
nitrate of silver into sulphide of silver, which is a good conductor 
of the current. For the production of the sulphuretted hydrogen 
place in the box, which contains the mould to be metallized, a 
porcelain plate or dish filled with dilute sulphuric acid (1 acid to 
8 water), and add five or six pieces of iron pyrites the size of a 
hazelnut. The development of the gas begins immediately, and 
the box should be closed with a well-fitting cover to prevent 
inhaling the poisonous gas ; if possible, the work should be done 
in the open air or under a well-drawing chimney. The formation 
of the layer of sulphide of silver requires but a few minutes, and 
if not many moulds have to be successively treated, the acid is 
poured oif from the iron pyrites and clean water poured upon the 
latter so as not to cause useless development of gas. 

It has also been recommended to decompose the silver salt by 
vapors of phosphorus and to convert it into phosphide of silver, 
a solution of phosphorus in bisulphide of carbon being used for 
the purpose. The layer of silver salt is moistened with the solu- 
tion or exposed to its vapors. This method possesses, however, 
no advantage over the preceding, because, on the one hand, the 
phosphorous solution takes fire spontaneously, and, on the other, 
the odor of the bisulphide of carbon is still more offensive than 
that of sulphuretted hydrogen. 



GALVANOPLASTY. 339 

A somewhat modified method is given by Parkes as follows : 
Three solutions, A, B, C, are required. Solution A is prepared by 
dissolving 0.5 part of caoutchouc cut up in fine pieces in 10 parts 
of bisulphide of carbon and adding 4 parts of melted wax ; stir 
thoroughly, then add a solution of 5 parts of phosphorus in 60 
of bisulphide of carbon together with 5 of oil of turpentine and 

4 of pulverized asphalt; then thoroughly shake this mixture, A. 
Solution B consists of 2 parts by weight of nitrate of silver in 
600 of water; and solution C of 10 parts of chloride of gold in 
600 of water. The mould to be metallized is first provided with 
wires and then brushed over with, or immersed in, solution A, 
and after draining off, dried. The dry mould is then poured over 
with the silver solution (B) and suspended free for a few minutes 
until the surface shows a dark lustre. It is then rinsed in water 
and treated in the same manner with the chloride of gold solution 
(C), whereby it acquires a yellowish tone, when, after drying, it 
is sufficiently prepared for the reception of the deposit. Care 
must be taken in preparing solution A, as the bisulphide of car- 
bon containing phosphorus readily takes fire. 

Another method is as follows : Dissolve 5 parts, by weight, of 
wax in 5 of warm oil of turpentine, and add to the solution a 
mixture of 5 parts, by weight, of phosphorus, 1 of gutta-percha, 

5 of asphalt in 120 of bisulphide of carbon. When both are 
thoroughly mixed, add to the whole a solution of 4 parts, by 
weight, of gun-cotton in 60 of alcohol, and 60 of ether, and after 
thorough shaking allow to settle. The next day pour off the clear 
solution from the sediment, when the solution can at once be used. 
It is especially well adapted for coppering parts of plants, leaves, 
flowers, etc. 

Another method of metallization is as follows : Immerse the 
leaves, etc., in iodized collodion composed of 40 per cent, alcohol 
40 cubic centimetres, ether 60 cubic centimetres, potassium iodide 
1 gramme, gun-cotton 1 gramme. 

Allow the leaves, etc., to dry so that a firmly adhering layer is 
formed; then immerse them in a solution of 10 parts, by weight, 
of nitrate of silver in 100 of water, whereby a layer of iodide 
of silver is formed. Now expose the article thus treated for some 
time to the light, and then immerse it in the reducing fluid, con- 



340 ELECTRO-DEPOSITION OF METALS. 

sisting of water 500 parts, by weight, green vitriol 25, and acetic 
acid of 1.04 specific gravity 25. The reduction of silver now 
progresses rapidly and the articles are ready for coppering. In 
employing this process it must not be forgotten that the layer of 
collodion will not stand rough usage, and hence injury to it by 
touching with the hands and careless placing of the conducting 
wire have to be avoided. By operating with the necessary care, 
the results are very satisfactory and sure. Instead of the iodized 
collodion, a mixture of equal parts of white of egg and saturated 
solution of common salt may be used, the remainder of the pro- 
cess being the same as above described. 

Metallization by metallic powders. — In some cases metallization 
by metallic powders is to be preferred to black-leading or metal- 
lizing by the wet way. Metallic or bronze powders are metals in 
a state of exceedingly line powder of which, for galvanoplastic 
purposes, pure copper and brass powders only are of interest. 
Since such metallic powders adhere badly to waxed surfaces, the 
mould must be provided with a well-drying coat of lacquer, upon 
which, before it is completely dry, the powder is scattered or sifted. 
When the lacquer is hard a smooth surface is produced by going 
over the mould with a soft brush dipped in the metallic powder, 
an excess being removed by a thin jet of water. 

Lenoir's process — Galvanoplastic method for originals in high 
relief. — Lenoir's method for reproducing statues in a manner 
approaches in principle to that of the foundry. He begins by 
making with gutta-percha a mould in several pieces, which are 
united together so as to form a perfect hollow mould of the origi- 
nal. This having been done, cover all the parts carefully with 
black-lead. Make a skeleton with platinum wire, following the 
general outline of the model, but smaller than the mould, since 
it must be suspended in it without any point of contact. If the 
skeleton thus prepared is enclosed in the metallized gutta-percha 
mould, and the whole immersed in the galvanoplastic bath, it will 
be sufficient to connect the inner surface of the mould with the 
negative pole of the battery, and the skeleton of platinum wires 
(which should have no points of contact with the metallized sur- 
face of the mould) with the positive pole, in order to decompose 
the solution of sulphate of copper which fills the mould. When 



GALVANOPLASTY. 341 

the metallic deposit has reached the proper thickness, the gutta- 
percha mould is removed by any convenient process, and a faith- 
ful copy of the original will be reproduced. Lead wires may be 
substituted for the expensive platinum wires. This method re- 
quires a knowledge of the moulder's art, so that good results can 
only be obtained by an experienced hand. 

Gelatine moulds. — Under certain conditions the elasticity of 
gelatine allows of the possibility of its removal from undercut or 
highly-wrought portions of the model, when it reassumes the 
shape and position it had before removal therefrom. But gela- 
tine requires that the deposit shall be made rapidly, otherwise it 
will swell and be partially dissolved by too long an immersion 
in the copper bath. 

To make a good gelatine mould proceed as follows : Allow white 
gelatine (cabinet-maker's glue) to swell for about 24 hours in cold 
water, then drain off the water, and heat the swollen mass in a water 
bath until completely dissolved. Compound the glue solution 
with pure glycerine in the proportion of 5 to 10 cubic centimetres 
(0.24 to 0.3 cubic inch) of glycerine to 30 grammes (1.05 ozs.) 
of gelatine, which prevents the gelatine from shrinking in cool- 
ing. When somewhat cooled off, apply the gelatine to the oiled 
original, which must be surrounded with a rim of plaster of Paris 
or wax, to prevent the gelatine from running off; when cold lift 
the gelatine mould from the model. Before metallizing and sus- 
pending in the copper bath, the mould has to be prepared to resist 
the action of the latter, as otherwise it would at once swell and be 
partially dissolved before being covered with the deposit. This 
is effected by placing the mould in a highly concentrated solution 
of tannin, which possesses the property of making gelatine inso- 
luble. 

Brandley gives the following directions for preparing gelatine 
solution with an addition of taunin, which renders the moulds 
impervious to water: Dissolve 20 parts of the best gelatine in 
100 of hot water, add J part of tannic acid and the same quan- 
tity of rock candy, then mix the whole thoroughly, and pour it 
upon the model. 

The same end is reached by making a mould with gelatine 
alone, then pouring an aqueous solution of 10 per cent, of bichro- 



342 ELECTKO-DEPOSITION OF METALS. 

mate of potassium upon it, and, after draining, exposing the mould 
to the action of the sun. 

Another method is as follows : Beat into a quart of distilled 
water the whites of two eggs, filter and cover with this liquid the 
entire surface of the gelatine mould. After drying, operate with 
the solution of bichromate of potassium as in the preceding. The 
solar action renders the coating impregnated with bichromate 
insoluble. 

The mould must finally be metallized and, when in the bath, 
submitted to a strong current at the beginning. When the entire 
surface is covered with the copper deposit, and when swelling is 
no longer to be feared, a weaker current may be used. 

In the following a few special uses of galvanoplasty will be 
briefly described : — 

Nature printing, so named by Mr. v. Auer, Director of the 
Imperial Printing Office at Vienna, has for its object the galvano- 
p^tic reproduction of leaves and other similar bodies. The leaf 
is placed between two plates, one of polished steel, the other of 
soft lead, and is then passed between rollers, which exert a con- 
siderable pressure. The leaf thus imparts an exact impression 
of itself and of all its veins and markings to the lead, and this 
impression may be electrotyped, and the copper plate produced 
used for printing in the ordinary way. Instead of taking the 
impression in lead, it is advisable to use gutta-percha or wax for 
delicate objects, which should previously be black-leaded or oiled. 
In the same manner galvanoplastic copies of laces, etc., may be 
obtained. 

The process used by Philipp for coating laces and tissues with 
copper and then silvering or gilding, belongs rather to electro- 
plating than to galvanoplasty. The tissue is saturated with 
melted wax, and after removing the excess with blotting paper 
it is made conductive by black-leading with a brush. It is 
however preferable to metallize such delicate objects by the wet 
way, Parke's method (p. 338) being especially suitable for the 
purpose, and also a treatment with weak solution of nitrate of 
silver and pyrogallic acid frequently alternated. 

Corvin's niello. — Corvin has invented a process of producing 
inlaid work by galvanoplasty, which has been patented, and is 



G ALVA XOPL AST Y. 343 

now the exclusive property of J. P. Kayser & Son, of Crefeld. 
The process is as follows : A matrice of metal whose surface is 
finely polished is first made. This matrice may be used for the 
production of numerous duplicates of the same kind of object. 
The incrustations (mother-of-pearl, glass, ivory, amber, etc.) are 
then shaped by means of a saw, files, and other tools to the form 
corresponding to that which they are to occupy in the design. 
The side of the incrustation which is laid upon the matrice is, 
as a rule, smooth. The shaped incrustations, smooth side down, 
are pasted on to the parts of the model they are to occupy in the 
design. The latter being thus produced, the backs of the non- 
metallic 'laminse are metallized, and the portions of the metallic 
plate left free are slightly oiled. By now placing the matrice 
thus prepared in the galvanoplastic bath, the copper is deposited 
not only upon the metallic matrice, but also upon the back of 
the inlaid pieces, the latter being firmly inclosed by the deposited 
metal. When the deposited metal has acquired the desired thick- 
ness it is detached from the matrice, and incrustations with the 
right side polished are thus obtained. The laminae are more 
accurately and evenly laid in than would be possible by the 
most skilled hand-work. 

Grasses, leaves, flowers, etc., may be coated with copper and then 
silvered, gilded, or platinized, by first drying them, and, after 
giving them a certain elasticity by placing in glycerine, metal- 
lizing them by Parkes's or some other method. 

Plates for the production of imitations of leather are now fre- 
quently prepared. The demand for alligator and similar leathers 
is at the present time greater than the supply, and, therefore, imi- 
tations are made by pressing ox-leather, the plate being prepared 
by galvanoplasty, as follows: A large piece of the natural skin 
or leather is made impervious to the bath by repeated coatings 
with lacquer, and, when completely dry, secured with asphalt 
lacquer to a copper or brass plate. The leather is then black- 
leaded and, after being made conductive by copper wire or small 
lead plates, brought into the copper bath. When the copper de- 
posit has acquired the desired thickness, the plate is further 
strengthened by backing with stereotype metal. 



344 ELECTRO-DEPOSITION OF METALS. 

To coat wood, etc., with a galvanoplastic deposit of copper. — The 
absolutely dry objects are first immersed in melted wax, paraffine, 
or ceresine, and when thoroughly impregnated taken out and, 
after draining off, allowed to cool. As the impregnating material 
contracts in cooling, the surface of the object is thereby freed from 
an excess of it. For this reason the material used for impreg- 
nating should not be made hotter than absolutely necessary, be- 
cause the hotter it is the stronger the contraction or shrinkage. 
However, as by this contraction the edges and portions of the 
surface may become denuded of impregnating material, and thus 
be liable to be attacked by the acid copper bath, it is advisable to 
coat the objects, after cooling, with an acid-resisting gutta-percha 
lacquer prepared by dissolving 5 to 10 parts, by weight, of gutta- 
percha cuttings in a mixture of 50 parts each of benzine and 
chloroform. Keep the solution in a wide-mouthed glass bottle 
provided with a well-fitting cork, and apply it with a brush. 
The solution being very inflammable it should not be used near 
an open flame. 

Wooden handles of surgical instruments, etc., may be protected 
from the attacks of the acid copper bath by coating them with a 
solution of wax or paraffine in ether, the latter after evaporating 
leaving a thin layer of wax upon the object. 

The articles thus prepared are black-leaded or metallized by 
Parkes's or one of the methods previously given, and brought into 
the copper bath. 

The mercury vessels of thermometers for vacuum and distilling 
apparatus are surrounded by a thick copper deposit to protect them 
from injury by mechanical force. The metallization of glass, 
porcelain, clay, terra-cotta, etc., is effected in the same manner as 
above described. 

Galvanoplastic operations in iron. — Under "Deposition of iron," 
page 293, the galvanoplastic production of heavy deposits of iron 
has already been referred to, it being there, also, mentioned that 
according to the researches of various authors a neutral solution of 
If ozs. of ammonio-ferrous sulphate in 1 quart of water is best 
adapted for the purpose, whilst Klein recommends a solution of 
equal parts of ferrous sulphate and sulphate of magnesia. To 
obtain an any way successfully iron electrotype from an original, 



GALVANOPLASTY. 345 

for instance, from a copper plate, which should previously be 
oiled and then Coated by means of sulphuretted hydrogen with 
a thin layer of sulphide of silver, the following conditions have 
to be fulfilled : The bath must be kept absolutely neutral accord- 
ing to one of the methods given on page 294, under formulae III. 
and IV. Further, the current-strength must be so regulated that 
absolutely no evolution of gas on the object is perceptible, and 
the distance of the anodes from the objects, which in the begin- 
ning of the operation may be If inches, must, according to Stam- 
mer, be gradually decreased to 0.19 inch. Furthermore, in the 
beginning of the operation the plates must at least every half 
hour be taken from the bath and rinsed off with a strong jet of 
water to remove adhering bubbles, the same object being attained 
by others by brushing the plates over with a feather. While out 
of the bath the plates must not be allowed to dry, as the fresh 
layers would not adhere to the places which have become dry. 
Now, even by strictly fulfilling the above-mentioned conditions, 
a faultless electrotype will be obtained only in one case out of 
five, this fact being mentioned in order to prevent practical electro- 
platers from wasting time and labor upon this process, which has 
not yet been sufficiently investigated and worked out. However, 
the interesting conditions for the production of heavy iron de- 
posits present a field of research and observation to those who 
need not follow galvanoplasty for a living. In making such re- 
searches it should be especially observed whether useful heavy 
deposits can be obtained from iron baths in. motion. 

Galvanoplastic operations in nickel. — Though by the electro- 
deposition of nickel, electrotypes are rendered fit for printing 
with metallic colors, which attack copper, and their power of 
resisting wear is increased, the latter advantage can to the fullest 
extent be obtained only by a thick deposit. However, this always 
alters the design somewhat, especially the fine hatchings, this 
being the reason why in electro-nickelling electrotypes a deposit 
of medium thickness is, as a rule, not exceeded. If a hard nickel 
surface is desired, without injury to the fine lines of the design, 
the layer of nickel has to be reproduced by galvanoplasty, and 
the deposit of nickel strengthened in the copper bath. 

But upon black-leaded gutta-percha or wax moulds a nickel 



346 ELECTRO-DEPOSITION OF METALS. 

deposit can only be obtained in fresh baths ; the deposit, how- 
ever, is faultless only in rare eases, it generally showing holes in 
the depressions. Hence the object has to be attained in a round- 
about way, the mode of procedure being as follows : An impres- 
sion of the original is taken in gutta-percha or wax and from this 
impression a positive cliche in copper is made. The latter is then 
silvered, the silvering iodized as previously described, and a nega- 
tive in copper is then prepared from this positive. The negative 
is again silvered, iodized, and then brought into a nickel bath 
where it receives a deposit of the thickness of stout writing-paper ; 
it is then rinsed in water, and the deposit immediately strengthened 
in the acid copper bath ; for the rest it is treated like ordinary 
copper deposits. Nickel electrotypes thus made are almost in- 
destructible. 

Galvanoplastic operations in silver and gold. — The preparation 
of reproductions in silver and gold also presents many difficulties. 
While copper is separable in a compact state from its sulphate 
solution, silver and gold have to be reduced from their double 
salt solutions — potassium silver cyanide aud potassium auric 
cyanide. However, these alkaline solutions attack moulds of fatty 
substances, such as wax and stearine, consequently also plaster-of- 
Paris moulds impregnated with these substances, as well as gutta- 
percha and gelatine. Hence, only metallic moulds can be advan- 
tageously used except the end is to be attained in a roundabout 
way ; that is, by first coating the mould with a thin film of cop- 
per, strengthening this in the silver or gold bath and finally dis- 
solving the film of copper with very dilute nitric acid. 

The double salt solutions mentioned above require a well-con- 
ducting surface such as cannot be readily prepared by black-lead- 
ing, a further reason why metallic moulds are to be preferred. 
The simplest way for the galvanoplastic reproduction in gold or 
silver of surfaces not in high relief or undercut, is to cover the 
object with lead, silver, or gold foil, and pressing softened gutta- 
percha upon it; the foil yields to the pressure without tearing 
and adheres to the gutta-percha so firmly that it can be readily 
separated together with it. Galvanoplastic reproductions in the 
noble metals are so seldom made in practice that it is not neces- 



COLORING, ETC., OF METALS. LACQUERING. 347 

sary to give further details. The composition of the baths gen- 
erally used is as follows : — 

Bath for galvanoplastie operations with silver. — Fine silver (in 
the form of silver cyanide or chloride of silver) If ozs., 98 per 
cent, potassium cyanide b\ ozs., water 1 quart. 

Bath for galvanoplastie operations with gold. — Fine gold (in the 
form of neutral chloride of gold) 1 oz., potassium cyanide 3| ozs., 
water 1 quart. 



CHAPTER XV. 

COLORING, PATINIZING, OXIDIZING, ETC., OF METALS. 

LACQUERING. 

Though, strictly speaking, these operations do not form a 
part of a work on the electro-deposition of metals, they require 
to be mentioned, since the operator is frequently forced to make 
use of one or the other method in order to furnish basis-metals 
or electro-deposits in certain shades of colors ordered. 

By patina is understood the beautiful green color antique 
statues and other art-works of bronze acquire by long exposure 
to the action of the oxygen, carbonic acid, and moisture of the 
air, whereby a thin layer of copper carbonate is formed upon 
them. It has been sought to accelerate by chemical means the 
formation of the patina thus slowly produced by the influence of 
time, and the term patinizing has been applied to this artificial 
production of colors. Without drawing a strict line as to which 
processes have to be considered as coloring, and which as patiniz- 
ing, the most approved methods for changing the color of the 
metals or of the deposits will be given. 

1. Coloring of copper. — All shades from the pale-red of copper 
to a dark chestnut-brown can be obtained by superficial oxidation 
of the copper. For small objects it suffices to heat them uniformly 
over an alcohol flame ; with larger objects a more uniform result 
is obtained by heating them in oxidizing fluids or brushing them 
over with an oxidizing paste, the best results being obtained with 
a paste prepared, according to the darker or lighter shade desired, 



348 ELECTRO-DEPOSITION OF METALS. 

from 2 parts of ferric oxide and 1 part of black-lead, or 1 part 
each of ferric oxide and black-lead, with alcohol or water. Apply 
the paste as uniformly as possible with a brush and place the 
object in a warm place (oven or drying chamber). The darker 
the color is to be the higher the temperature must be, and the 
longer it must act upon the object. When sufficiently heated the 
dry powder is removed by brushing with a soft brush, and the 
manipulation repeated if the object does not show a sufficiently 
dark tone. Finally the object is rubbed with a soft linen rag 
moistened with alcohol, or brushed with a soft brush and a few 
drops of alcohol until completely dry, and then with a brush 
previously rubbed upon pure wax. The more or less dark shade 
produced in this manner is very warm and resists the action of 
the air. 

Brown color upon copper is obtained by applying to the 
thoroughly cleansed surface of the object a paste of verdigris 
3 parts, ferric oxide 3, sal ammoniac 1, and sufficient vinegar, 
and heating until the applied mixture turns black ; the object is 
then washed and dried. By the addition of some blue vitriol the 
color may be darkened to chestnut-brown. 

A brown color is also obtained by brushing to dryness with a 
hot solution of 1 part of potassium nitrate, 1 of common salt, 2 
of ammonium chloride, and 1 of liquid ammonia in 95 of vinegar. 
A warmer tone is, however, produced by the method introduced 
in the Paris Mint, which is as follows : Powder and mix inti- 
mately equal parts of verdigris and sal ammoniac. Take a heap- 
ing tablespoonful of this mixture and boil it with water in a 
copper kettle for about twenty minutes and then pour off the 
clear fluid. To give copper objects a bronze-like color with this 
fluid pour part of it into a copper pan ; place the objects sepa- 
rately in it upon pieces of wood or glass, so that they do not touch 
each other, or come in contact with the copper pan, and then boil 
them in the liquid for a quarter of an hour. Then take the 
objects from the solution, rub them dry with a linen cloth, and 
brush them with a waxed brush. 

A red-brown color on copper is produced in China by the appli- 
cation of a paste of verdigris 2 parts, cinnabar 2, sal ammoniac 5, 



COLORING, ETC., OF METALS. LACQUERING. 349 

and alum 5, with sufficient vinegar, heating over a coal fire, wash- 
ing and repeating the process. 

Copper is colored blue-black by dipping the object in a hot solu- 
tion of 11 J drachms of liver of sulphur in 1 quart of water, 
moving it constantly. Blue-gray shades are obtained with more 
dilute solutions. It is difficult to give definite directions as to 
the length of time the solution should be allowed to act, since this 
depends on its temperature and concentration. With some expe- 
rience the correct treatment, however, will soon be learned. 

The so-called cuivre fume is produced by coloring the copper 
or coppered objects blue-black with solution of liver of sulphur, 
then rinsing, and finally scratch-brushing them, whereby the 
shade becomes somewhat lighter. From raised portions which 
are not to be dark, but are to show the color of copper, the color- 
ation is removed by polishing upon a felt wheel or bob. 

Black color upon copper is produced by a heated pickle of 2 
parts of arsenic acid, 4 of concentrated muriatic acid, 1 of sul- 
phuric acid of 66° Be., and 21 of water. 

Dead-black on copper. — Brush the object over with a solution 
of 1 part of platinum chloride in 5 of water, or dip it in the solu- 
tion. A similar result is obtained by dipping the copper object 
in a solution of nitrate of copper or of manganese, and drying 
over a coal fire. These manipulations are to be repeated until 
the formation of a uniform dead-black. 

Imitation of genuine patina. — Repeatedly brush the objects with 
solution of sal ammoniac in vinegar ; the action of the solution 
being accelerated by the addition of verdigris. A solution of 9 
drachms of sal ammoniac and 2| drachms of potassium binoxalate 
in 1 quart of vinegar acts still better. When the first coating is 
dry, wash the object, and repeat the manipulations, drying and 
washing after each application, until a green patina is formed. It 
is best to bring the articles after being brushed over with the 
solution into a hermetically closed box upon the bottom of which 
a few shallow dishes containing very dilute sulphuric or acetic 
acid and a few pieces of marble are placed. Carbonic acid being 
thereby evolved and the air in the box being kept sufficiently 
moist by the evaporation of water, the conditions required for the 
formation of genuine patina are thus fulfilled. If the patina is 



350 ELECTRO-DEPOSITION OF METALS. 

to show a more bluish tone, brush the object with a solution of 
4^ ozs. of ammonium carbonate and 1 J ozs. of sal ammoniac in 
1 quart of water, to which a small quantity of gum tragacanth 
may be added. 

To produce a steel-gray color upon copper immerse the clean 
and pickled objects in a heated solution of chloride of antimony 
in hydrochloric acid. By using a strong electric current the 
objects may also be coated with a steel-gray deposit of arsenic in 
a heated arsenic bath. 

For coloring copper dark steel-gray, a pickle consisting of 1 
quart of hydrochloric acid, 0.125 quart of nitric acid, 1J ozs. of 
arsenious acid, and a like quantity of iron tilings is recommended. 

Various colors upon massive copper. — First draw the object 
through a pickle composed of sulphuric acid 60 parts, hydro- 
chloric acid 24.5, and lampblack 15.5; or of nitric acid 100 
parts, hydrochloric acid 1J, and lampblack J. Then dissolve 
in a quart of water 4| ozs. of sodium hyposulphite, and in 
another quart of water 14J drachms of blue vitriol, 5J drachms 
of crystallized verdigris, and 7f grains of sodium arsenate. Mix 
equal volumes of the two solutions, but no more than is actually 
necessary for the work in hand, and heat to between 167° and 
176° F. By dipping articles of copper, brass, or nickel in the hot 
solution they become immediately colored with the colors men- 
tioned below, one color passing within a few seconds into the 
other, and for this reason the effect must be constantly controlled 
by frequently taking the objects from the bath. The colors suc- 
cessively formed are as follows : — 



Upon copper: 


Upon brass : 


Upon nickel: 


Orange, 


Golden-yellow, 


Yellow, 


Terra-cotta, 


Lemon color, 


Blue, 


Red (pale), 


Orange, 


Iridescent. 


Blood-red, 


Terra-cotta, 




Iridescent. 


Olive-green. 





Some of these colors not being very durable, have to be pro- 
tected by a coat of lacquer or paraffine. It is further necessary 
to diligently move the objects, so that all portions acquire the 



COLORING, ETC., OF METALS. — LACQUERING. 351 

same color. The bath decomposes rapidly, and hence only suffi- 
cient for 2 or 3 hours' use should be mixed at one time. 

2. Coloring of brass and bronzes. — Most of the directions given 
for coloring copper are also available for brass and bronzes, 
especially those for the production of the green patina, and the 
oxidized tones by a mixture of ferric oxide and black-lead. 

Many colorations on brass, however, are effected only with 
difficulty, and are partially entirely unsuccessful, as, for instance, 
coloring black with liver of sulphur. As a pickle for the pro- 
duction of a :- — 

Lustrous black on brass, the following solution may be used : 
Dissolve freshly precipitated carbonate of copper, while still 
moist, in strong liquid ammonia, using sufficient of the copper 
salt so that a small excess remains undissolved, or, in other words, 
that the ammonia is saturated with copper. The carbonate of 
copper is prepared by mixing hot solutions of equal parts of blue 
vitriol and of soda, filtering off, and washing the precipitate. 

Dilute the solution of the copper salt in ammonia with one- 
fourth its volume of water, add 31 to 46 grains of black-lead, 
and heat to between 95° and 104° F. Place the clean and 
pickled objects in this pickle for a few minutes, until they show 
a full black shade, then rinse in water, dip in hot water and dry 
in sawdust. The solution soon spoils, and hence no more than 
required for immediate use should be prepared. 

Another method of coloring brass black has been given under 
"Deposition of Arsenic," p. 298. 

Urquhart states that clean brass and copper may be covered 
with a firmly adherent black coating by placing them very near 
to the flames of burning straw. It will not rub off', and may be 
polished with a soft cloth. 

Steel-gray on brass is obtained by the use of a mixture of 1 lb. 
of strong hydrochloric acid with 1 pint of water, to which are 
added 5^ ozs. of iron filings and a like quantity of pulverized 
antimonic sulphide. 

Hydrochloric acid compounded with arsenious acid is also 
recommended for this purpose. The mixture is brought- into a 
lead vessel, and the objects dipped in it should come in contact with 
the lead of the vessel, or be wrapped around with a strip of lead. 



352 ELECTRO-DEPOSITIOX OF METALS. 

A gray color with, a bluish tint upon brass is produced with 
solution of antimouious chloride (butter of antimony), while a 
pure steel-gray color is obtained with a hot solution of arsenious 
chloride with a little water. 

Straw color, to brown, through golden yellow, and tombac color on 
brass may be obtained with solution of carbonate of copper in 
caustic soda lye. Dissolve 5.25 ozs. of caustic soda in 1 quart of 
water, and add If ozs. of carbonate of copper. By using the 
solution cold, a dark golden-yellow is first formed, which finally 
passes through pale brown into dark brown with a green lustre ; 
with the hot solution the coloration is more rapidly effected. 

A color resembling gold or brass is, according to Dr. Kayser, 
obtained as follows : Dissolve 8| drachms of sodium hyposulphite 
in 17 drachms of water, and add 5.64 drachms of solution of anti- 
monious chloride. Heat the mixture to boiling for some time, 
then filter off the red precipitate formed, and after washing it 
several times upon the filter with vinegar, suspend it in 2 or 3 
quarts of hot water ; then heat and add concentrated soda lye 
until solution is complete. In this hot solution dip the clean and 
pickled brass objects, removing them frequently to see whether 
they have acquired the desired coloration. The articles become 
gray by remaining too long in the bath. 

Brown color, called bronze Barbedienne, on brass. — This beauti- 
ful color may be produced as follows : Dissolve by vigorous shak- 
ing in a bottle, freshly prepared arsenious sulphide in spirit of sal 
ammoniac, and compound the solution with autimonious sulphide 
until a slight permanent turbidity shows itself, and the fluid has 
acquired a deep yellow color. Heat the solution to 95° F., and 
suspend the brass objects in it. They become at first golden- 
yellow and then brown, but as they come from the bath with a 
dark dirty tone, they have to be several times scratch-brushed to 
bring out the color. If, after using it several times, the solution 
fails to work satisfactorily, add some antimonious sulphide. The 
solution decomposes rapidly, and should be prepared fresh every 
time it is to be used. 

By this method only massive brass objects can be colored 
brown ; to brassed zinc and iron the solution imparts brown- 
black tones, which, however, are also quite beautiful. 



COLORING, ETC., OF METALS. LACQUERING. 353 

Upon massive brass, as well as upon brassed zinc and iron 
objects, bronze Barbedienne may be produced as follows : Mix 
3 parts of red sulphide of antimony (stibium sulfuratum auranti- 
anum) with 1 part of finely pulverized bloodstone, and triturate 
the mixture with ammonium sulphide to a not too thickly-fluid 
pigment. Apply this pigment to the objects with a brush, and, 
after allowing it to dry in a drying chamber, remove the powder 
by brushing with a soft brush. 

In Paris bronze articles are colored dead-yellow or clay-yellow 
to darh-bro%vn by first brushing the pickled and thoroughly rinsed 
objects with dilute antimony bisulphide, and, after drying, re- 
moving -the coating of separated sulphur by brushing. Dilute 
solution of sulphide of arsenic in ammonia is then applied, the 
result being a color resembling mosaic gold. The more frequently 
the arsenic solution is applied, the browner the color becomes. By 
substituting for the arsenic solution one of sulphide of antimony 
in ammonia or ammonium sulphide, colorations of a more reddish 
tone are obtained. 

Violet- and corn-flower blue upon brass may be produced as 
follows : Dissolve in 1 quart of water 4| ozs. of sodium hypo- 
sulphite, and in another quart of water 1 oz. 3f drachms of 
crystallized sugar of lead, and mix the solutions. Heat the 
mixture to 176° F., and then immerse the articles, moving them 
constantly. First a gold-yellow coloration appears, which, how- 
ever, soon passes into violet and blue, and if the bath be allowed 
to act further, into green. The action is based upon the fact that 
in an excess of hyposulphite of soda solution of hyposulphite of 
lead is formed, which decomposes slowly and separates sulphide 
of lead, which precipitates upon the brass objects and produces 
the various lustrous colors. 

Similar lustrous colors are obtained by dissolving 2.11 ozs. of 
pulverized tartar in 1 quart of water, and 1 oz. of chloride of 
tin in J pint of water, mixing the solutions, heating, and pouring 
the clear mixture into a solution of 6.34 ozs. of sodium hyposul- 
phite in 1 pint of water. Heat this mixture to 176° F., and 
immerse the pickled brass objects. 

JEberrnayer's experiments in coloring brass. — In the following the 
results of Ebermayer's experiments are given. In testing the 
23 



354 ELECTEO-DEPOSITIOX OF METALS. 

directions, the same results as those claimed by Ebermayer were 
not always obtained ; and variations are given in parentheses. 

I. Blue vitriol 8 parts by weight, crystallized sal ammoniac 2, 
water 100, give by boiling a greenish color. (The color is olive- 
green, and useful for many purposes. The coloration however 
succeeds only upon massive brass, but not upon brassed zinc.) 

IT. Potassium chlorate 10 parts by weight, blue vitriol 10, water 
1000, give by boiling a brown-orange to cinnamon-brown color. 
(Only a yellow-orange color could be obtained.) 

III. By dissolving 8 parts by weight of blue vitriol in 1000 
of water, and adding 100 of caustic soda until a precipitate is 
formed, and boiling the objects. in the solution, a gray-brown 
color is obtained, which can be made darker by the addition of 
colcothar. (Stains are readily formed. Brassed zinc acquires a 
pleasant pale-brown.) 

IV. With 50 parts by weight of caustic soda, 50 of sulphide of 
antimony, and 500 of water, a pale, jig-broivn color is produced. 
(Fig-brown could not be obtained, the shade being rather dark 
olive-green.) 

V. By boiling 400 parts by weight of water, 25 of sulphide of 
antimony, and 60 of calcined soda, and filtering the hot solution 
mineral kermes is precipitated. By taking of this 5 parts by 
weight and heating with 5 of tartar, 400 of water, and 10 of 
sodium hyposulphite, a beautiful steel-gray is obtained. (The re- 
sult is tolerably sure and good.) 

VI. Water 400 parts by weight, potassium chlorate 20, nickel 
sulphide 10, give after boiling for some time a brown color, which, 
however, is not formed if the sheet has been pickled. (The brown 
color obtained is not very pronounced.) 

VII. Water 250 parts by weight, potassium chlorate 5, carbo- 
nate of nickel 2, and sulphate of ammonium and nickel 5, give 
after boiling for some time a brown-yellow color, playing into a 
magnificent red. (The results obtained were only indifferent.) 

VIII. Water 250 parts by weight, potassium chlorate 5, and 
sulphate of nickel and ammonium 10, give a beautiful dark brown. 
(Upon massive brass a good dark-brown is obtained. The for- 
mula, however, is not available for brassed zinc.) 



COLORING, ETC., OF METALS. LACQUERING. 355 

3. Coloring zinc. — The results obtained by coloring zinc directly 
according to existing directions cannot be relied on, and it is, 
therefore, recommended to first copper the zinc and then color 
the coppering. Experiments in coloring zinc black with alcoholic 
solution of chloride of antimony according to Dullas's process gave 
no useful results. Puscher's method is better ; according to it the 
objects are dipped in a boiling solution of 5.64 ozs. of pure green 
vitriol and 3.17 ozs. of sal ammoniac in 2| quarts of water. The 
loose black precipitate deposited upon the objects is removed by 
brushing, the object again dipped in the hot solution and then 
held over a coal fire until the sal ammoniac evaporates. By re- 
peating the operation three or four times a firmly adhering black 
coating is formed. To color zinc black with nitrate of manga- 
nese, as proposed by Neumann, is a tedious operation, it requiring 
to be repeated seven or eight times. It is done by dipping the 
object in a solution of nitrate of manganese and heating over a 
coal fire, the manipulations being repealed until a uniform dead- 
black is obtained. 

By suspending zinc in a nickel bath slightly acidulated with 
sulphuric acid, a firmly adhering blue-black coating is, after some 
time, formed without the use of a current. This coating is use- 
ful for many purposes. A similar result is attained by immers- 
ing the zinc objects in a solution of 2.11 ozs. of the double 
sulphate of nickel and ammonium and a like quantity of sal 
ammoniac in 1 quart of water. The articles become first dark 
yellow, then, successively, brown, purple-violet, and indigo-blue, 
and stand slight scratch-brushing and polishing. 

A gray coating on zinc is obtained by a deposit of arsenic in a 
heated bath composed of 2.82 ozs. of arsenious acid, 8.46 drachms 
of sodium pyrophosphate, and 1 § drachms of 98 per cent, potassium 
cyanide and 1 quart of water. A strong current should be used 
so that a vigorous evolution of hydrogen is perceptible. Platinum 
sheets or carbon plates are used as anodes. 

A sort of bronzing on zinc is obtained by rubbing it with a 
paste of pipe-clay to which has been added a solution of 1 part 
by weight of crystallized verdigris, 1 of tartar, and 2 of crystal- 
lized soda. 



356 ELECTRO-DEPOSITION OF METALS. 

Red-brown color on zinc. — Rub with solution of chloride of 
copper in liquid ammonia. 

Yellow-brown shades on zinc. — Rub with solution of chloride of 
copper in vinegar. 

4. Coloring of iron. — The browning of gun-barrels is effected 
by the application of a mixture of equal parts of butter of 
antimony and olive oil. Allow the mixture to act for 12 to 14 
hours, then remove the excess with a woollen rag and repeat the 
application. When the second application has acted for 12 to 24 
hours, the iron or steel will be coated with a bronze-colored layer 
of ferric oxide with antimony, which resists the action of the air 
and may be made lustrous by brushing with a waxed brush. 

A lustrous black on iron is obtained by the application of 
solution of sulphur in spirits of turpentine prepared by boiling 
upon the water bath. After the evaporation of the spirits of 
turpentine a thin layer of sulphur remains upon the iron, which, 
on heating the object, immediately combines with the metal. 

By another method the cleansed and picked iron objects are 
coated, when dry, with linseed oil, and heated to a dark red. If 
pickling is omitted^ the coating with linseed oil and heating may 
have to be repeated two or three times. 

According to Meritens, a lustrous black on iron is obtained by 
placing the articles as anode in distilled water heated to 158° F., 
and using an iron plate as cathode. A layer of ferroso- ferric 
oxide is formed, which, however, can be obtained in a firmly 
adhering state only upon wrought-iron. The lustre appears by 
brushing with a soft waxed brush. The current conducted into 
the bath must be just strong enough to decompose the water with- 
out perceptible evolution of gas. 

According to Bottger a durable blue on iron and steel may be 
obtained by dipping the article in a ^ per cent, solution of red 
prussiate of potash mixed with an equal volume of a i per cent, 
ferric chloride solution. 

A brown-black coating with bronze lustre on iron is obtained by 
heating the bright iron objects and brushing them over with con- 
centrated solution of potassium bichromate. When dry, heat 
them over a charcoal fire and wash until the water running off 
shows no longer a yellow color. Repeat the operation twice or 



COLORING, ETC., OF METALS. — LACQUERING. 357 

three times. A similar coating is obtained by heating the iron 
objects with a solution of 10 parts by weight of green vitriol and 
1 part of sal ammoniac in water. 

To give iron a silvery appearance with high lustre. — Scour the 
polished and pickled iron objects with a solution prepared as fol- 
lows : Heat moderately 1 J ozs. of chloride of antimony, 0.35 oz. 
of pulverized arsenious acid, 2.82 ozs. of elutriated bloodstone 
with 1 quart of 90 per cent, alcohol upon a water bath for half 
au hour. Partial solution takes place. Dip into this fluid a tuft 
of cotton and go over the iron portions, using slight pressure. 
A thin film of arsenic and antimony is thereby deposited, which 
is the more lustrous the more carefully the iron has been previ- 
ously polished. 

5. Coloring of tin. — A bronze-like patina on tin may be obtained 
by brushing the object over with a solution of If ozs. of blue 
vitriol and a like quantity of green vitriol in 1 quart of water, 
and moistening the object when dry with a solution of 3J ozs. of 
verdigris in 10| ozs. of vinegar. When dry, polish the object 
with a soft waxed brush and some ferric oxide. The coating thus 
obtained being not especially durable, must be protected by a coat- 
ing of lacquer. 

Durable and very warm sepia-brown tone upon tin and its 
alloys. — Brush the object over with a solution of 1 part of platinum 
chloride in 10 of water, allow the coating to dry, then rinse in 
water, and, after again drying, brush with a soft brush until the 
desired brown lustre appears. 

A dark coloration is also obtained with ferric chloride solution. 

6. Coloring of silver. — See "Silvering," p. 242. 

Lacquering. 

In the electro-plating industry recourse is frequently had to 
lacquering in order to make the deposits more resistant against 
atmospheric influences, or to protect artificially prepared colors, 
patinas, etc. Thin, colorless shellac solution, which does not affect 
the color of the deposit or of the patinizing, is, as a rule, em- 
ployed, while in some cases colored lacquers are used to heighten 
the tone of the deposit, as, for instance, gold lacquer for brass. 



358 ELECTRO-DEPOSITION OF METALS. 

The lacquer is applied by means of a fine flat fitch-brush, the 
object having previously been heated hand- warm. After lacquer- 
ing the object is dried in an oven at a temperature of between 
140° and 158° F., whereby small irregularities are adjusted, and 
the layer of lacquer becomes transparent, clear, and lustrous. 

Cellulose lacquers and varnishes. — Under the name of zapon a 
dip-lacquer has been introduced in commerce. It represents a 
clear, almost colorless fluid of the consistency of collodion, and 
smells something like fruit ether. According to G. Buchner, it 
consists essentially of a solution of cellulose in a mixture of amyl 
acetate and acetone. Of the last two bodies, the "thinning 
fluid," which accompanies the preparation, also consists. This 
lacquer can be highly recommended, its superiority being due to 
the favorable properties of the cellulose. The transparent, color- 
less coat obtained with zapon can be bent with the metallic sheet, 
to which it has been applied, without cracking. It is so hard that 
it can scarcely be scratched with the finger-nail, shows no trace 
of stickiness, and it is perfectly homogeneous even on the edges. 
This favorable behavior is very likely due to the slow evaporation 
of the solvent, and the fact that the lacquer quickly forms a 
thickish, tenacious layer, which, though moved with difficulty, is 
not entirely immobile. Another advantage of zapon — especially 
as regards metallic objects — is that the coating, in consequence of 
its physical constitution, preserves the character of the basis. In 
accordance with the nature of cellulose, the coating is not sensi- 
bly affected by ordinary differences in temperature, and does not 
become dull and non-transparent, as is the case with resins, in 
consequence of the loss of molecular coherence. It can be washed 
with soap and water, and protects metals coated with it from the 
action of the atmosphere. Zapon may also be colored, but, of 
course, only with coloring substances — mostly aniline colors — 
which are soluble in the solvent used for the cellulose. 

A similar preparation is known as Jcristaline. It is a hard, 
transparent enamel, which can be applied as a lacquer in all kinds 
of metal-work without affecting the most delicate finish. It is 
applied by dipping, is invisible, and leaves no mark in drying. 

Kristaline has now been in use for about ten years, and can be 
relied upon to protect all metal-work from acids and alkalies, also 



COLORING, ETC., OF METALS. LACQUERING. 



359 



coal-gas, alcohol, benzine, oil, water, fly-specks, etc. It is espe- 
cially designed to prevent the highest class of metal-work from 
tarnishing and preserve the delicate shades of color produced by 
electricity and artificial oxidation. 

In coating articles with zapon or kristaline no special skill or 
apparatus is necessary ; but to obtain the best results the manu- 

Fig. 130. 




facturers have adopted a form of closet or drying rack, shown in 
Fig. 130. 

A lacquer similar to zapon or kristaline may be prepared by 
substituting soluble pyroxylin for cellulose, the process being as 
follows : Bring collodion-cotton, i. e., soluble pyroxylin, such as 
is used by photographers, into a box which can be hermetically 
closed, and place upon the bottom of the box a dish with sul- 
phuric acid. The purpose of this is to dry the collodion-cotton, 
which requires from 36 to 48 hours. The collodion -cotton is then 
brought into a large bottle, and three to four times its quantity 
by weight of very strong alcohol poured over it. In a few days 
the greater portion of it is dissolved, when the clear solution is 
poured into another bottle. Add to the clear solution more collo- 
dion-cotton, about 25 to 30 per cent, of the weight of the quan- 
tity originally used, and the resulting product forms an excellent 
cellulose lacquer, which rapidly hardens to a perfectly transparent 



360 ELECTRO-DEPOSITION OF METALS. 

aud very glossy coating. For diluting cellulose lacquers it is best 
to use wood spirit. To color them, dissolve an aniline color in 
strong spirits of wine, add a corresponding quantity of the solu- 
tion to the lacquer, and shake vigorously. 

In conclusion, a few words may be said in regard to the pro- 
cesses by which those magnificent effects are obtained which imitate 
so completely the appearance, freshness, and rich tones of real gild- 
ing. In general, gold varnish is applied only upon copper and 
its more or less yellow alloys. 

Gold varnishers operate as follows : After the objects have been 
perfectly cleansed, scratch-brushed, and burnished, if necessary, 
they are completely dried in hot sawdust and wiped clean with 
a fine cloth. A light coat of varnish is then applied with a fitch- 
pencil, and all excess of varnish removed or levelled with another 
flat brush of badger-hair or bristles. The two brushes are kept 
together in the same hand, the varnish brush between the thumb 
and first two fingers, while the flat one (without a handle) is held 
between the other fingers and the palm of the hand. In this 
manner there is no interval in the use of the two brushes. The 
varnish is kept in a jelly-pot or other similar vessel, across the top 
of which a string has been stretched. This string is intended for 
removing by wiping the excess of varnish taken up by the brush 
or pencil. The varnish which covers the burnished parts of the 
object may be removed with a clean rag moistened with alcohol 
and wrapped round the finger. Another dry cloth finishes the 
drying. Sometimes the burnished parts are also varnished, but 
the operation is very difficult when their surface is considerable. 
Round-ware, polished or burnished, may be varnished in the lathe. 

After the varnish has been applied as uniformly as possible, the 
objects are put in a drying stove heated to between 140° and 175° 
F. The alcohol or essential oils of the varnish are rapidly vola- 
tilized, while the resins or gums melt and cover the objects with 
a glassy lustre. The heat must be sufficient to melt these gums, 
but low enough to avoid burning them. When the operation has 
been well performed, the pieces present a beautiful and uniform 
golden appearance, with no disfiguring red patches, which latter 
indicate an unequal thickness of varnish. 

Varnishers have always at their disposal four varnishes of dif- 



HYGIENIC RULES FOR THE WORKSHOP. 361 

ferent shades — red gold, orange-yellow gold, green gold,, and color- 
less varnish for mixture. This last is employed for diluting the 
first three and diminishing the depth of their colors. Each of 
these various varnishes gives to copper the gold color peculiar 
to it, and, when mixed, intermediary shades. It often happens 
that the various parts of a large piece are different in composition 
and color, and the varnisher is obliged to impart the same shade 
of gold all over by skilful combinations of varnishes. He thus 
succeeds in giving the same gold color to half-red copper and to 
alloys of yellow and green brass. 

But a small quantity of varnish is poured into the varnish pot 
at one time, to prevent it from thickening by evaporation, and 
after the operation the residue is poured back into the flask from 
which it was taken and kept well stoppered. The brushes and 
pencils must be often washed in alcohol, which may afterwards 
be used for diluting thick varnishes. 

These varnishes are made by dissolving various resinous sub- 
stances, like sandarac, benzoin, dragon's-blood, elemi, gamboge, 
etc., and tinctorial matters, such as saffron, annotto, alkanet, etc. 
in a mixture of alcohol with essence of lavender or of spikenard. 
All qualities of varnish are to be found, but the more expensive 
are often the more economical. 

To remove the varnish from an imperfectly varnished object 
or from an old one it is immersed in alcohol or concentrated sul- 
phuric acid, or, better still, in a boiling solution of caustic lye. 
The varnishing is then begun anew. 



CHAPTER XVI. 

HYGIENIC RULES FOR THE WORKSHOP. 

In but few other branches of the industry has the workman so 
constantly to deal with powerful poisons, as well as other sub- 
stances and vapors, which are exceedingly corrosive in their action 
upon the skin and the mucous membranes, as in electro-plating. 
However, with the necessary care and sobriety, all influences in- 
jurious to health may be readily overcome. 



362 ELECTRO-DEPOSITION OF METALS. 

The necessity of frequently renewing the air in the workshop 
by thorough ventilation has already been referred to in Chapter 
IV., "Electro-plating establishments in general." Workmen 
exclusively engaged in pickling objects are advised to neutralize 
the action of the acid upon the enamel of the teeth and the 
mucous membrane of the mouth and throat by frequently rinsing 
the mouth with dilute solution of bicarbonate of soda. Workmen 
engaged in freeing the objects from grease lose, for want of cleanli- 
ness, the skin on the portions of the fingers which come constantly 
in contact with the lime and caustic lyes. This may be overcome 
by frequently washing the hands in clean water, and previous to 
each intermission in the work the workman should after washing 
the hands dip them in dilute sulphuric acid, dry them, and 
thoroughly rub them with cosmoline or a mixture of equal parts 
of glycerine and water. The use of rubber gloves by workmen 
engaged in freeing the objects from grease cannot be recommended, 
they being expensive and subject to rapid destruction. It is better 
to wrap a linen rag seven or eight times around a sore finger, 
many workmen using this precaution to protect the skin from the 
corrosive action of the lime. 

It should be a rule for every workman employed in an electro- 
plating establishment not to drink from vessels used in electro- 
plating manipulations ; for instance, porcelain dishes, beer glasses, 
etc. One workman may this moment use such a vessel to drink 
from and without his knowledge another may employ it the next 
moment for dipping out potassium cyanide solution, and the first 
using it again as a drinking vessel may incur sickness or even fatal 
poisoning. The handling of potassium cyanide and its solutions 
requires constant care and judgment. Working with sore hands 
in such solutions should be avoided as much as possible ; but if 
it has to be done, and the workman feels a sharp pain in the sore, 
wash the latter quickly with clean water and apply a few drops 
of green vitriol solution. Many individuals are very sensitive to 
nickel solutions, eruptions, which are painful and heal slowly, 
breaking out upon the arms and hands, while others may for 
years come in contact with nickel baths without being subject to 
such eruptions. In such case prophylaxis is also the safeguard, 
i. e., to prevent by immediate thorough washing the formation of 



HYGIENIC RULES FOR THE WORKSHOP. 363 

the eruption if the skin has been brought in contact with nickel 
solution, as, for instance, in taking out with the hand an object 
fallen into a nickel bath. 

In the following, some directions will be found for neutralizing, 
in case of internal poisoning, the effects of the poison either en- 
tirely or at least sufficiently to retard its action until professional 
aid can be summoned. 

Poisoning by hydrocyanic (prussic) acid, potassium cyanide, or 
cyanides. — If prussic acid, or the cyanides, be concentrated or have 
been absorbed in considerable quantity, their action is almost 
instantly fatal, and there is little hope of saving the victim, 
although everything possible should be tried. But if these sub- 
stances have been taken in very dilute condition, they may not 
prove immediately fatal, and there is some hope that remedial 
measures may be successfully applied. 

In poisoning, with these substances water as cold as possible 
should be run upon the head and spine of the patient, and he 
should be made to inhale, carefully and moderately, the vapor of 
chlorine water, bleaching powder, or Javelle water (hypochlorite 
of soda). 

Should these poisons be introduced into the stomach, there should 
be administered as soon as possible the hydrate of sesquioxide of 
iron, or, what is better, dilute solutions of the acetate, citrate, or 
tartrate of iron. With proper precautions a very dilute solution 
of sulphate of zinc may be given. 

Poisoning by copper-salts. — The stomach should be quickly 
emptied by means of an emetic or, in want of this, the patient 
should thrust his finger to the back of his throat and induce 
vomiting by tickling the uvula. After vomiting drink milk, 
white of egg, gum-water, or some mucilaginous decoction. 

Poisoning by lead-salts requires the same treatment as poisoning 
by copper-salts. Lemonade of sulphuric acid, or an alkaline solu- 
tion containing carbonic acid, such as Vichy water, or bicarbonate 
of soda, is also very serviceable. 

Poisoning by arsenic. — The stomach must be quickly emptied 
by an energetic emetic, when freshly precipitated ferric hydrate 
and calcined magnesia may be given as an antidote. Calcined 



361 ELECTRO-DEPOSITION OF METALS. 

magnesia being generally on hand, mix it with 15 to 20 times the 
quantity of water and give of this mixture 3 to 6 tablespoonfuls 
every 10 to 15 minutes. 

Poisoning by alkalies. — Use weak acids, such as vinegar, lemon- 
juice, etc., and in their absence sulphuric, hydrochloric, or nitric 
acid diluted to the strength of lemonade. After the pain in the 
stomach has diminished, it will be well to administer a few spoon- 
fuls of olive oil. 

Poisoning by mercury- salts. — Mercury salts, and particularly the 
chloride (corrosive sublimate), form with the white of egg (albumen) 
a compound very insoluble and inert. The remedy is therefore 
indicated. Sulphur and sulphuretted water are also serviceable 
for the purpose. 

Poisoning by sulphuretted hydrogen. — The patient should be 
made to inhale the vapor of chlorine from chlorine water, Javelle 
water, or bleaching-powder. Energetic friction, especially at the 
extremities of the limbs, should be employed. Large quantities 
of warm and emollient drinks should be given and abundance of 
fresh air. 

Poisoning by chlorine, sulphurous acid, nitrous a,nd hyponitric 
gases. — Admit immediately an abundance of fresh air, and ad- 
minister light inspirations of ammonia. Give plenty of hot drinks 
and excite friction, in order to conserve the warmth and transpira- 
tion of the skin. Employ hot foot-baths to remove the blood from 
the lungs. Afterwards maintain in the mouth of the patient some 
substance which, melting slowly, will keep the throat moist, such 
as jujube and marshmallow paste, molasses candy, and liquorice 
paste. Milk is excellent. 



PRODUCTS USED IN ELECTRO-PLATING. 365 



CHAPTER XVII. 

CHEMICAL PRODUCTS AND VARIOUS APPARATUS AND 
INSTRUMENTS USED IN ELECTRO-PLATING. 

A. Chemical Products. 

In the following the characteristic properties of the chemical 
products employed in the workshop will be briefly discussed, and 
the reactions indicated which allow of their recognition. It fre- 
quently happens that the labels become detached from the bottles 
and boxes, thus rendering the determination of their contents 
necessary. 

I. Acids. 

1. Sulphuric acid (oil of vitriol). — Two varieties of this acid 
are found in commerce, viz., fuming sulphuric acid (disulphuric 
acid), and ordinary sulphuric acid. The first is a thick oily fluid 
generally colored yellowish by organic substances, and emits dense 
white vapors in the air. Its specific gravity is 1.87 to 1.89. The 
only purpose for which fuming sulphuric acid is used in the 
electro-plating art is as a mixture with nitric acid, for stripping 
silvered objects. 

Ordinary sulphuric acid has a specific gravity of 1.84. Diluted 
with water it serves for filling the Bunsen elements and as a pickle 
for iron ; in a concentrated state it is used in the preparation of 
pickles and as an addition to the galvanoplastic copper bath. 
The crude commercial acid generally contains arsenic, hence care 
must be had to procure a pure article. In diluting the acid with 
water, it should in all cases be added to the water in a very gentle 
stream and with constant stirring, as otherwise a sudden genera- 
tion of steam of explosive violence might result, and the danger- 
ous corrosive liquid be scattered in all directions. Concentrated 
sulphuric acid vigorously attacks all organic substances, and hence 



366 ELECTRO-DEPOSITION OF METALS. 

has to be kept in bottles with glass stoppers, and bringing it in 
contact with the skin should be carefully avoided. 

Recognition. — One part of acid mixed with 25 parts of distilled 
water gives, when compounded with a few drops of barium chloride 
solution, a white precipitate of barium sulphate. 

2. Nitric acid (aqua fortis, spirit of nitre). — It is found in trade 
of various degrees of strength ; for our purposes acid of 40° 
and 30° Be., being generally used. The acid is usually a more or 
less deep yellow, and frequently contains chlorine. The vapors 
emitted by nitric acid are poisonous and of a characteristic odor, 
by which the concentrated acid is readily distinguished from other 
acids. It is used for filling the Bunsen elements, and for pickling 
in combination with sulphuric acid and chlorine. On coming in 
contact with the skin it produces yellow stains. 

Recognition. — By heating the not too dilute acid with copper, 
brown-red vapors are evolved. For the determination of dilute 
nitric acid, add a few drops of it to green vitriol solution, when 
a black-brown coloration will be produced on the point of con- 
tact. 

3. Hydrochloric acid (muriatic acid). — The pure acid is a color- 
less fluid which emits abundant fumes in contact with the air, and 
has a pungent odor by which it is readily distinguished from other 
acids. The specific gravity of the strongest hydrochloric acid is 
1.2 ; the crude acid of commerce has a yellow color, due to iron, 
and contains arsenic. Dilute hydrochloric acid is used for pickling 
iron and zinc. 

Recognition — On adding to the acid strongly diluted with 
distilled water a few drops of solution of nitrate of silver in dis- 
tilled water a heavy white precipitate is formed, which becomes 
black by exposure to the light. 

4. Hydrocyanic acid [prussic acid). — This extremely poisonous 
acid exists in nature only in a state of combination in certain 
vegetables and fruits, and especially in the kernels of the latter, 
as, for instance, in the peach, the berries of the cherry laurel, 
bitter almonds, the stones of the apricot, of plums, cherries, etc. 
It may be obtained anhydrous, but in this state it is useless, and 
very difficult to preserve from decomposition. Diluted hydro- 
cyanic acid is colorless, with a bitter taste and the characteristic 



PRODUCTS USED IN ELECTRO-PLATING. 367 

smell of bitter almonds. It is employed in the preparation of 
gold immersing baths, and for the decomposition of the potassa 
in old silver baths. The inhalation of the vapors of this acid 
may have a fatal effect, as also its coming in contact with wounds. 
Recognition. — By its characteristic smell of bitter almonds. Or 
mix it with potash lye until blue litmus paper is no longer red- 
deued, then add solution of green vitriol which has been partially 
oxidized by standing in the air, and acidulate with hydrochloric 
acid. A precipitate of Berlin blue is formed. 

5. Citric acid. — Clear colorless crystals of 1 .542 specific gravity, 
which dissolve with great ease in both hot and cold water. It is 
frequently employed for acidulating nickel baths and, combined 
with sodium citrate, in the preparation of platinum baths. 

Recognition. — Lime-water compounded with aqueous solution 
of citric acid remains clear in the cold, but on boiling deposits a 
precipitate of calcium citrate. This precipitate is soluble in 
ammonium chloride, but on boiling is again precipitated, and is 
then insoluble in sal ammoniac. 

6. Boric acid (boracic acid). — This acid is found in commerce 
in the shape of scales with nacreous lustre and greasy to the 
touch ; when obtained from solutions by evaporation, it forms 
colorless prisms. Its specific gravity is 1.435; it dissolves with 
difficulty in cold water (1 part of acid requiring, at 64.4° F., 28 
of water), but is more rapidly soluble in boiling water (1 part of 
acid requiring 3 of water at 212° F.). According to Weston's 
proposition, boric acid is employed as an addition to nickel baths, 
etc. 

Recognition. — By mixing solution of boric acid in water with 
some hydrochloric acid and dipping turmeric paper in the solution, 
the latter acquires a brown color, the color becoming more intense 
on drying. Alkalies impart to turmeric paper a similar coloration, 
which, however, disappears on immersing the paper in dilute 
hydrochloric acid. 

7. Arsenious acid, {white arsenic, arsenic, ratsbane). — It generally 
occurs in the shape of a white powder and sometimes in vitreous- 
like lumps, resembling porcelain ; for our purposes the white 
powder is almost exclusively used. It is slightly soluble in cold 
water, and more readily in hot water and hydrochloric acid. Not- 



368 ELECTRO-DEPOSITION OF METALS. 

withstanding its greater specific gravity (3.7) only a portion of 
the powder sinks to the bottom on mixing it with water, another 
portion being retained on the surface by air bubbles adhering to 
it. It is employed as an addition to brass baths, further, in the 
preparation of arsenic baths, for blacking copper alloys, and in 
certain silver whitening baths. 

Recognition. — When some arsenious acid is thrown upon glow- 
ing coals an odor resembling that of garlic is perceptible. By 
mixing solution of arsenious acid, prepared by boiling with water, 
with a few drops of ammoniacal solution of nitrate of silver, a 
yellow precipitate of arsenate of silver is obtained. The ammo- 
niacal solution of nitrate of silver is prepared by adding ammonia 
to solution of nitrate of silver until the precipitate at first formed 
disappears. 

8. Chromic acid. — It forms crimson-red needles, and also occurs 
in commerce in the shape of a red powder. It is readily soluble 
in water, forming a red fluid which serves for filling batteries. 

Recognition — Chromic acid can scarcely be mistaken for any 
other chemical product employed by the electro-plater. A strongly 
diluted solution of it gives, after neutralizing with caustic alkali 
and adding a few drops of nitrate of silver solution, a crimson- 
red precipitate of chromate of silver. 

II. Alkalies and Alkaline Earths. 

9. Potassium hydrate (caustic potash).— It is found in commerce 
in various degrees of purity, either in sticks or cakes. It is very 
deliquescent and dissolves readily in water and alcohol ; by ab- 
sorbing carbonic acid from the air it rapidly becomes converted 
into the carbonate and thus loses its caustic properties. It should, 
therefore, be stored in well-closed vessels. Substances moistened 
with solution of caustic potash give rise to a -peculiar soapy 
sensatiou of the skin when touched. It should never be allowed to 
enter the mouth, as even dilute solutions almost instantaneously re- 
move the lining of tender skin. Should such an accident happen, 
the mouth should be at once several times rinsed with water and 
then with very dilute acetic acid. Pure caustic potash serves as 
an addition to zinc baths, gold baths, etc. For the purpose of 



PRODUCTS USED IN ELECTRO-PLATING. 369 

freeing objects from grease the more impure commercial article is 
used. 

1 0. Sodium hydrate (caustic soda). — It also occurs in commerce 
in various degrees of purity, either in sticks or lumps. It is of a 
highly caustic character resembling potassium hydrate (see above) 
in properties and effects. It is employed for freeing objects from 
grease. 

11. Ammonium hydrate {ammonia or spirits of hartshorn). — It is 
simply water saturated with ammonia gas. By exposure ammonia 
gas is gradually evolved, so that it must be stored in closely- 
stoppered bottles in order to preserve the strength of the solution 
unimpaired. Four qualities are generally found in commerce, viz., 
ammonia of 0.910 specific gravity (containing 24.2 per cent, of 
ammonia gas); of 0.920 specific gravity (with 21.2 per cent, of 
ammonia gas); of 0.940 specific gravity (with 15.2 per cent, of 
ammonia gas) ; and 0.960 specific gravity (with 9.75 per cent, of 
ammonia gas). It is employed for neutralizing nickel and cobalt 
baths when too acid, in the preparation of fulminating gold, and 
as an addition to some copper and brass baths. 

Recognition. — By the odor. 

12. Calcium hydrate (burnt or quick lime). — It forms hard, 
white to gray pieces, which on moistening with water crumble to 
a light white powder, evolving thereby much heat. Vienna lime 
is burnt lime containing magnesia. Lime serves for freeing ob- 
jects from grease, and for this purpose is made into a thinly-fluid 
paste with chalk and water with which the objects to be freed 
from grease are brushed. Vienna lime is much used as a polish- 
ing agent. 

III. Sulphur Combinations. 

13. Sulphuretted hydrogen (sulphydric acid, hydrosidphuric 
acid). — A very poisonous colorless gas with a fetid smell resem- 
bling that of rotten eggs. Ignited in the air it burns with a blue 
flame, sulphurous acid and water being formed. At the ordinary 
temperature water absorbs about three times its own volume of 
the gas, and then acquires the same properties as the gas itself. 
Sulphuretted hydrogen serves for the metallizing of moulds as 

24 



370 ELECTRO-DEPOSITION OF METALS. 

described on p. 338, where the manner of evolving it is also 
given. It is sometimes employed for the production of "oxidized" 
silver. Bringing not only metallic salts, but gilt or silvered arti- 
cles, or pure gold and silver, in contact with sulphuretted hydro- 
gen, should be carefully avoided, they being rapidly sulphurized 
by it. 

Recognition. — By its penetrating smell ; further, by a strip of 
paper moistened with sugar of lead solution becoming black when 
brought into a solution or an atmosphere containing sulphuretted 
hydrogen. 

14. Potassium sulphide (liver of sulphur). — It forms a hard 
green-yellow to pale brown mass, with conchoidal fracture; it 
readily absorbs moisture, whereby it deliquesces and smells of 
sulphuretted hydrogen. It is employed for coloring copper and 
silver black. 

Recognition. — On pouring an acid over liver of sulphur sulphu- 
retted hydrogen is evolved with effervescence, sulphur being at 
the same time separated. 

15. Ammonium sulphide (sidphydrate or hydrosulphate of am- 
monia). — When freshly prepared it forms a clear and colorless 
fluid, with an odor of ammonia and sulphuretted hydrogen ; by 
standing it becomes yellow, and, later on, precipitates sulphur. 
It is used for the same purpose as liver of sulphur. 

16. Carbon disulpkide or bisulphide. — Pure carbon disulphide 
is a colorless and transparent liquid, which is very dense, and 
exhibits the property of double refraction. Its smell is charac- 
teristic and most disgusting, and may be compared to that of 
rotten turnips. It burns with a blue flame of sulphurous acid, 
carbonic acid being at the same time produced. It is used as 
a solvent for phosphorus and caoutchouc in metallizing moulds 
according to Parkes's method. This solution should be very care- 
fully handled. 

17. Antimony sulphide. — a. Black sulphide of antimony (stibium 
sulfuratum nigrum) is found in commerce in heavy, gray, and 
lustreless pieces or as a fine black-gray powder, with slight lustre. 
It serves for the preparation of antimony baths, and for coloring 
copper alloys black. 



PRODUCTS USED IN ELECTRO-PLATING. 371 

b. Red sulphide of antimony (stibium sulfuratum aurantiacum) 
forms a delicate orange-red powder without taste or odor ; it is 
insoluble in water, but soluble in ammonium sulphide, spirits of 
hartshorn, and alkaline lyes. In connection with ammonium sul- 
phide or ammonia it serves for coloring brass brown. 

18. Arsenic trisulphide or arsenious sulphide (orpiment). — It is 
found in commerce in the natural as well as artificial state, the 
former occurring mostly in kidney-shaped masses of a lemon 
color, and the latter in more orange-red masses, or as a dull yellow 
powder. Specific gravity 3.46. It is soluble in the alkalies and 
spirits of .sal ammoniac. 

19. Ferric sidphide. — Hard black masses generally in flat plates 
which are only used for the evolution of sulphuretted hydrogen. 

IV. Chlorine Combinations. 

20. Sodium chloride (common salt, roch salt). — The pure salt 
should form white cubical crystals, of which 100 parts of cold 
water dissolve 36, hot water dissolving slightly more. The 
specific gravity of sodium chloride is 2.2. In electroplating 
sodium chloride is employed as a conducting salt for some gold 
baths, as a constituent of argentiferous pastes, and for precipitating 
the silver as chloride from argentiferous solutions. 

Recognition. — An aqueous solution of sodium chloride on being 
mixed with a few drops of lunar caustic solution yields a white 
caseous precipitate, which becomes black by exposure to light and 
does not disappear by the addition of nitric acid, but is dissolved 
by ammonia in excess. 

21. Ammonium chloride (sal ammoniac). — A white substance 
found in commerce in the shape of tough fibrous crystals. It 
has a sharp saline taste, and is soluble in 2f parts of cold, and in 
a much smaller quantity of hot water. By heat it is sublimed 
without decomposition. It serves for soldering and tinning, and 
as a conducting salt for many baths. 

Recognition. — By the sublimation on heating. By adding to a 
saturated solution of the salt a few drops of solution of platinum 
chloride, a yellow precipitate of platoso-ammonium chloride is 
formed. 



372 ELECTKO-DEPOS1TION OF METALS. 

22. Antimony trichloride (butter of antimony). — A crystalline 
mass which readily deliquesces in the air. Its solution in hydro- 
chloric acid yields the liquor stibii chlorati, also called liquid butter 
of antimony ; it has a yellowish color, and on mixing with water 
yields an abundant white precipitate soluble in potash lye. The 
solution serves for coloring brass steel-gray, and for browning 
gun-barrels. 

23. Arsenious chloride. — A thick oily fluid, which evaporates 
in the air with the emission of white vapors. 

24. Copper chloride. — Blue-green crystals readily soluble in 
water. The concentrated solution is green, and the dilute solu- 
tion blue. On evaporating to dryness, brown-yellow copper 
chloride is formed. It is employed in copper and brass baths as 
well as for patinizing. 

25. Tin chloride. — a. Stannous chloride or tin salt. A white 
crystalline salt readily soluble in water, but its solution on ex- 
posure to the air becomes turbid; by adding, however, hydro- 
chloric acid, it again becomes clear. On fusing the crystallized 
salt it loses its water of crystallization, and forms a solid non- 
transparent mass of a pale-yellow color — the fused tin salt. The 
crystallized, as well as the fused, salt serves for the preparation 
of brass, bronze, and tin baths. 

Recognition. — By pouring hydrochloric acid over a small quan- 
tity of tin salt and adding potassium chromate solution, the solu- 
tion acquires a green color. By mixing dilute tin salt solution 
with some % chlorine water and adding a few drops of gold 
chloride solution, purple of Cassius is precipitated ; very dilute 
solutions acquire a purple color. 

b. Stannic chloride occurs in commerce in colorless crystals, and 
in the anhydrous state forms a yellowish, strongly fuming caustic 
liquid known as the " fuming liquor of Libadius." 

26. Zinc chloride (hydrochlorate or muriate of zinc ; butter of 
zinc). — A white crystalline or fused mass which is very soluble 
and deliquescent. The salt prepared by evaporation generally 
contains some zinc oxychloride, and hence does not yield an 
entirely clear solution. It serves for preparing brass and zinc 
baths, and its solution for nickelling by immersion, soldering, etc. 



PRODUCTS USED IN ELECTRO-PLATING. 373 

Recognition. — Solution of caustic potash separates a voluminous 
precipitate of zinc oxy hydrate, which redissolves in an excess of 
the caustic potash solution. By conducting sulphuretted hydrogen 
into a solution of a zinc salt acidulated with acetic acid, a precipi- 
tate of white zinc sulphide is formed. 

27. Zinc chloride and ammonium chloride. — This salt is a com- 
bination of zinc chloride with sal ammoniac, and forms a white 
very deliquescent powder. Its solution serves for soldering and 
for zincking by contact. 

28. Nickel chloride. — It is found in commerce in the shape of 
deep green crystals and of a pale green powder ; the latter con- 
tains considerably less water and less free acid than the crystallized 
article, and is to be preferred for electro-plating purposes. The 
crystallized salt dissolves readily in water, and the powder some- 
what more slowly ; should the solution of the latter deposit a 
yellow precipitate, consisting of basic nickel chloride, it has to be 
brought into solution by the addition of a small quantity of hydro- 
chloric acid. Nickel chloride is employed for nickel baths. 

Recognition. — By mixing the green solution of the salt with 
some spirits of sal ammoniac, a precipitate is formed which dis- 
solves in an excess of spirits of sal ammoniac, the solution show- 
ing a deep blue color. 

29. Cobalt chloride. — It forms small rose-colored crystals, 
which, on heating, yield their water of crystallization and are 
converted into a blue mass. The crystals are readily soluble in 
water, while the anhydrous blue powder dissolves slowly. Cobalt 
chloride is employed for the preparation of cobalt baths. 

Recognition. — Caustic potash precipitates from a solution of 
cobalt chloride a blue basic salt which is gradually converted into 
a rose-colored hydrate, and, with the access of air, into green- 
brown cobaltous hydrate ; the aqueous solution yields with solu- 
tion of yellow prussiate of potash a pale gray-green precipitate. 

30. Silver chloride (horn silver). — A heavy white powder gradu- 
ally passing, by exposure to white light, through a gradation of 
shades from violet to black. By precipitation from silver solu- 
tions it separates as a caseous precipitate (p. 245). At 500° F. it 
melts, without decomposing, to a yellowish fluid, which, on cool- 
ing, congeals to a transparent, tenacious, horn-like mass. Chloride 



374 ELECTRO-DEPOSITION OF METALS. 

of silver is practically insoluble in water, but dissolves readily in 
spirits of sal ammoniac and in potassium cyanide solution. It is 
employed in the preparation of baths for electro-silvering, for the 
whitening baths, and for the pastes for silvering by friction. 

Recognition. — By its solubility in ammonia, pulverulent metallic 
silver being separated from the solution by dipping in it bright 
ribbands of copper. 

31. Gold chloride {ter chloride of gold, muriate of gold, auric 
chloride). — This salt occurs in commerce as crystallized gold 
chloride of an orange-yellow color, and as a brown crystalline 
mass, which is designated as neutral gold chloride, or as gold 
chloride free from acid, whilst the crystallized article always con- 
tains acid, and, hence, should not be used for gold baths. Gold 
chloride absorbs atmospheric moisture and becomes resolved into 
a liquid of a fine gold color. On being moderately heated 
yellowish-white aurous chloride is formed, and on being subjected 
to stronger heat it is decomposed to metallic gold and chlorine 
gas. By mixing its aqueous solution with ammonia, a yellow- 
brown powder consisting of fulminating gold is formed. In a dry 
state this powder is highly explosive, and, hence, when precipi- 
tating it from gold chloride solution for the preparation of gold 
baths, it must be used while still moist. 

Recognition. — By the formation of the precipitate of fulminating 
gold on mixing the gold chloride solution with ammonia. Further 
by the precipitation of brown metallic gold powder on mixing 
the gold chloride solution with green vitriol solution. 

32. Platinic chloride. — The substance usually known by this 
name is hydroplatinic chloride. It forms red-brown very soluble 
— and in fact deliquescent — crystals. With ammonium chloride 
it forms platoso-ammonium chloride (see p. 276). Both combina- 
tions are used in the preparation of platinum baths. The solu- 
tion of platinic chloride also serves for coloring silver, tin, brass, 
and other metals. 

Recognition. — By the formation of a precipitate of yellow platoso- 
ammonium chloride by mixing concentrated platinic chloride solu- 
tion with a few drops of saturated sal ammoniac solution. 



PRODUCTS USED IN ELECTRO-PLATING. 375 

V. Cyanides. 

33. Potassium cyanide (white prussiate of potash). — For electro- 
plating purposes pure potassium cyanide with 98 to 99 per cent., 
as well as that containing 80, 70, and 60 per cent., is used, whilst 
for pickling the preparation with 45 per cent, is employed. For 
the preparation of alkaline copper and brass baths, as well as 
silver baths, the pure 98 to 99 per cent, product is generally 
employed. However, for preparing gold baths the 60 per cent, 
article is mostly preferred, because the potash present in all potas- 
sium cyanide varieties with a lower content renders fresh baths 
more conductive. However, gold baths may also be prepared 
with 98 per cent, potassium cyanide without fear of injury to the 
efficiency of the baths, while, under ordinary circumstances, a 
preparation with less than 98 per cent, may safely be used for the 
rest of the baths. However, when potassium cyanide has to be 
added to the baths, as is from time to time necessary, only the 
pure preparation free from potash should be used, because the 
potash contained in the inferior qualities gradually thickens the 
bath too much. 

No product is more important to the electro-plater than potas- 
sium cyanide. The pure 98 to 99 per cent, product is a white 
transparent crystalline mass, the crystalline structure being plainly 
perceptible upon the fracture. In a dry state it is odorless, but 
when it has absorbed some moisture it has a strong smell of prus- 
sic acid. It is readily soluble in water, and should be dissolved 
in cold water only, since when poured into hot water it is partially 
decomposed, which is recognized by the appearance of an odor of 
ammonia. Potassium cyanide solution in cold water may, how- 
ever, be boiled for a short time without suffering essential decom- 
position. Potassium cyanide must be kept in well-closed vessels, 
being when exposed to the air deliquescent, and it is decomposed 
by the carbonic acid of the air, whereby potassium carbonate is 
formed while prussic acid escapes. It is a deadly poison and 
must be used with the utmost caution. Potassium cyanide with 
80, 70, 60, or 45 per cent, forms a gray-white to white mass 
with a porcelain-like fracture. A pale gray coloration is not a 
proof of impurities, it being due to somewhat too high a tern- 



376 ELECTRO-DEPOSITION OF METALS. 

perature in fusing. These varieties are found in commerce in 
irregular lumps or in sticks, the use of the latter offering no 
advantage. Their behavior towards the air and in dissolving is 
the same as that of the pure product. 

Recognition. — By the bitter almond smell of the solution. By 
mixing potassium cyanide solution with ferric chloride and then 
with hydrochloric acid until the latter strongly predominates, a 
precipitate of Berlin blue is formed. 

The pure salt free from potash does not effervesce on adding 
dilute acid, which is, however, the case with the inferior qualities. 

To facilitate the use of potassium cyanide with a different con- 
tent than that given in a formula for preparing a bath, the fol- 
lowing table is here given : — 

Potassium cyanide with 
98 per cent. 80 per cent. 70 per cent. GO per cent. 45 per cent. 

By weight. By weight. By weight. By weight. By weight. 

1 part = 1.230 parts = 1.400 parts = 1.660 parts = 2.180 parts. 
0.820 " =1 " =1.143 " =1.333 " =1.780 " 

0.714 " = 0.875 part = 1. part = 1.170 " = 1.550 " 
0.615 " = 0.750 " = 0.857 " =1 part = 1.450 " 
0.460 " = 0.562 " = 0.643 " = 0.750 " =1 part 

34. Copper cyanides. — There is a cuprous and a cupric cyanide ; 
that used for electro-plating purposes being a mixture of both. 
It is a green-brown powder, which shonld not be dried, since in 
the moist state it dissolves more readily in potassium cyanide. 
It is only used as a double salt, i. e., in combination with potas- 
sium cyanide in the preparation of copper, brass, tombac, and 
red gold baths. 

Recognition — By evaporating a piece of copper cyanide the size 
of a pea, or its solution in hydrochloric acid to dryness in a water 
bath, whereon care must be taken not to inhale the vapors, and 
dissolving the residue in water, a green-blue solution is obtained 
which acquires a deep blue color by the addition of ammonia in 
excess. 

35. Zinc cyanide (hydrocyanate of zinc, prussiate of zinc). — A 
white powder insoluble in water, but soluble in potassium cyanide, 



PRODUCTS USED IN ELECTRO-PLATING. 377 

ammonia and the alkaline sulphites; the fresher it is, the more 
readily it dissolves, the dried product dissolving with difficulty. 
Its solution in potassium cyanide is used for brass baths. 

Recognition. — By evaporating zinc cyanide or its solution in an 
excess of hydrochloric acid, zinc chloride remains behind, which 
is recognized by the reaction given under zinc chloride. 

36. Silver cyanide (prussiate, or hydrocyanate of silver). — A 
white powder which slowly becomes black when exposed to light. 
It is insoluble in water and cold acids, which, however, will dis- 
solve it with the aid of heat. At 750° F. it melts to a dark red 
fluid, which, on cooling, forms a yellow mass with a granular 
structure. It is readily dissolved by potassium cyanide, but is 
only slightly soluble in ammonia, differing in this respect from 
silver chloride. It forms a double salt with potassium cyanide, 
and as such is employed in the preparation of silver baths. 

37. Potassium ferro-cyanide (yellow prussiate of potash). — It 
occurs in the shape of yellow semi-translucent crystals with 
mother-of-pearl lustre, which break gradually and without noise. 
For the solution of 1 part of it, 4 of water are required, the 
solution exhibiting a pale yellow color. It precipitates nearly all 
the metallic salts from their solutions, some of the precipitates 
being soluble in an excess of the precipitating agent. This salt 
is not poisonous. It serves for the preparation of silver and gold 
baths; its employment, however, offering no advantages over 
potassium cyanide except its non-poisonous properties be con- 
sidered as such. 

Recognition. — When the yellow solution is mixed with ferric 
chloride a precipitate of Berlin blue is formed. 

VI. Carbonates. 

38. Potassium carbonate (potash). — It is found in commerce in 
gray-white, bluish, yellowish pieces, the colorations being due to 
admixtures of small quantities of various metallic oxides, and 
pure in the form of a white powder or in pieces the size of a pea. 
The salt, being very deliquescent, has to be kept in well-closed 
receptacles. It is readily soluble, and, if pure, the solution in 



378 ELECTRO-DEPOSITION OF METALS. 

distilled water must be clear. It serves as an addition to some 
baths, and in an impure state for freeing objects from grease. 

Recognition. — The solution effervesces on the addition of 
hydrochloric acid. The solution neutralized with hydrochloric 
acid gives with platinum chloride a heavy yellow precipitate, 
provided the solution be not too dilute. 

39. Acid potassium carbonate or monopotassic carbonate, com- 
monly called bicarbonate of potash. — Colorless transparent crys- 
tals, which at a medium temperature dissolve to a clear solution 
in 4 parts of water. It is not deliquescent ; however, on boiling 
its solution loses carbonic acid, and contains then only potassium 
carbonate. It is employed for the preparation of certain baths 
for gilding by simple immersion. 

40. Sodium carbonate (washing soda). — It occurs in commerce 
as crystallized or calcined soda of various degrees of purity. 
The crystallized product forms colorless crystals or masses of 
crystals, which, on exposure to air, rapidly effloresce and crumble 
to a white powder. By glowing, the crystals also lose their water, 
a white powder, the so-called calcined soda, remaining behind. 
Soda dissolves readily in water, and serves as an addition to 
copper and brass baths, for the preparation of metallic carbonates, 
and for freeing objects from grease, the ordinary impure soda 
being used for the latter purpose. 

The directions for additions of sodium carbonate to baths gene- 
rally refer to the crystallized salt. If calcined soda is to be used 
instead, 0.4 part of it will have to be taken for 1 part of the 
crystallized product. 

41. Sodium bicarbonate (baking powder). — A dull white powder 
soluble in 10 parts of water of 68° F. On boiling, the solution 
loses one-half of its carbonic acid, and then contains sodium car- 
bonate only. 

42. Calcium carbonate (marble, chalk). — -When pure it forms a 
snow-white crystalline powder, a yellowish color indicating a con- 
tent of iron. It is insoluble in water, but soluble, with efferves- 
cence, in hydrochloric, nitric, and acetic acids. In nature, calcium 
carbonate occurs as marble, limestone, chalk. 

In the form of whiting (ground chalk carefully freed from all 
stony matter) it is used for the removal of an excess of acid in 



PRODUCTS USED IN ELECTRO-PLATING. 379 

acid copper baths, and mixed with burnt lime as an agent for 
freeing objects from grease. 

43. Copper carbonate. — Occurs in nature as malachite and allied 
minerals. The artificial carbonate is an azure-blue substance, in- 
soluble in water, but soluble, with effervescence, in acids. Copper 
carbonate precipitated from copper solution by alkaline carbon- 
ates has a greenish color. Copper carbonate is employed for 
copper and brass baths, and for the removal of an excess of acid 
in acid copper baths. 

Recognition. — Dissolves in acids with effervescence ; on dipping 
a ribband of bright sheet-iron in the solution, copper separates 
upon the iron. On compounding the solution with ammonia in 
excess, a deep blue coloration is obtained. 

44. Zinc carbonate. — A white powder, insoluble in water. The 
product obtained by precipitating a zinc salt with alkaline carbo- 
nates is a combination of zinc carbonate with zinc oxyhydrate. 
It serves for brass baths in connection with potassium cyanide. 

Recognition. — In a solution in hydrochloric acid, which is 
formed with effervescence, according to the reactions given under 
zinc chloride (26). 

45. Nickel carbonate. — A pale apple-green powder, insoluble in 
water, but soluble, with effervescence, in acids. It is employed 
for neutralizing nickel baths which have become acid. 

Recognition. — In hydrochloric acid it dissolves, with efferves- 
cence, to a green fluid ; by the addition of a small quantity of 
ammonia, nickel oxyhydrate is precipitated, which, by adding am- 
monia in excess, is redissolved, the solution showing a blue color. 

46. Cobalt carbonate. — A reddish powder, insoluble in water, 
but soluble in acids, the solution forming a red fluid. 

VII. Sulphates and Sulpjliites. 

47. Sodium sulphate {Glauber's salt). — Clear crystals of a 
slightly bitter taste, which effloresce by exposure to the air. They 
are readily soluble in water. On heating, the crystals melt in 
their water of crystallization, and on glowing, calcined Glauber's 
salt remains behind. It is used as an addition to some baths. 



380 ELECTRO-DEPOSITION OF METALS. 

48. Ammonium sulphate. — It forms a neutral colorless salt, 
which is constant in the air, readily dissolves in water, and evapo- 
rates on heating. It serves as a conducting salt for nickel, cobalt, 
and zinc baths. 

Precognition. — By its evaporating on heating ; a concentrated 
solution compounded with platinic chloride gives a yellow pre- 
cipitate of platoso-ammonium. chloride, while a solution mixed 
with a few drops of hydrochloric acid gives with barium chloride 
a precipitate of barium sulphate. 

49. Aluminium-potassium sulphate (pjotash-alum). — Colorless 
crystals or pieces of crystals with an astringent taste. It is solu- 
ble in water, 12 parts of it dissolving in 100 parts of water at 
the ordinary temperature. On heating, the crystals melt, and are 
converted into a white spongy mass, the so-called burnt alum. 
Potash-alum serves for the preparation of zinc baths and for 
brightening the color of gold. 

Recognition. — On adding sodium phosphate to the solution a 
jelly-like precipitate of aluminium phosphate is formed, which is 
soluble in caustic potash, but insoluble in acetic acid. 

50. Ammonium- alum is exactly analogous to the above, the 
potassium sulphate being simply replaced by ammonium sulphate. 
It is for most purposes interchangeable with potash-alum. Ou 
glowing ammonium-alum the ammonium sulphate is lost, pure 
alumina remaining behind. Ammonium-alum is used for pre- 
paring a bath for zincking iron and steel by immersion. 

Recognition. — The same as potash-alum. On heating the com- 
minuted ammonium-alum with potash lye an odor of ammonia 
becomes perceptible. 

51. Iron sulphate (iron prolosulphate, ferrous sulphate or green 
vitriol). — Pure green vitriol forms bluish-green transparent crys- 
tals of a sweetish astringent taste, which readily dissolve in water. 
Crude green vitriol is a green crystalline substance, often yellow- 
ish on the exterior owing to the formation of ferric compounds 
with the aid of atmospheric oxygen. It generally contains, be- 
sides ferrous sulphate, the sulphates of copper and zinc as well as 
ferric sulphate. On account of the tendency to peroxidation, 
green vitriol and other ferrous compounds should not be exposed 
to the air any more than is necessary. Green vitriol is employed 



PRODUCTS USED IN ELECTRO-PLATING. 381 

for the preparation of iron baths, and for the reduction of gold 
from its solutions. 

Recognition. — By compounding the green solution with a few 
drops of concentrated nitric acid, a black-blue ring is formed on 
the point of contact. On mixing the lukewarm solution with 
gold chloride, gold is separated as a brown powder, which by rub- 
bing acquires the lustre of gold. 

52. Iron- ammonium sulphate. — Green crystals which are constant 
in the air and do not oxidize as readily as green vitriol. 100 parts 
of water dissolve 16 parts of this salt. It is used for the same 
purposes as green vitriol. 

53. Copper sulphate (cupric sulphate or blue vitriol). — It forms 
blue crystals, of which 100 parts of cold water dissolve about 40, 
and the same volume of hot water about 200 parts. Blue vitriol 
which does not possess a pure blue color, but shows a greenish 
lustre, is contaminated with green vitriol, and should not be used 
for electro-plating purposes. Blue vitriol serves for the prepa- 
ration of alkaline copper and brass baths, acid copper baths, etc. 

Recognition. — By its appearance, as it can scarcely be mistaken 
for anything else. A content of iron is recognized by boiling blue 
vitriol solution with a small quantity of nitric acid, and adding 
spirits of sal ammoniac in excess ; brown flakes indicate iron. 

54. Zinc sulphate (ichite vitriol). — It forms small colorless prisms 
of a harsh metallic taste, which readily oxidize on exposure to the 
air. By heating the crystals melt, and by glowing are decomposed 
into sulphurous acid and oxygen, which escape, while zinc oxide 
remains behind as residue. 100 parts of water dissolve about 50 
parts of zinc sulphate in the cold, and nearly 100 at the boiling- 
point. Zinc sulphate is employed for the preparation of brass 
and zinc baths. 

Recognition. — By mixing zinc sulphate solution with acetic acid 
and conducting sulphuretted hydrogen into the mixture, a white 
precipitate of zinc sulphide is formed. A slight content of iron 
is recognized by the zinc sulphate solution, made alkaline by am- 
monia, giving with ammonium sulphide a somewhat colored pre- 
cipitate instead of a pure white one. However, a slight content 
of iron does no harm. 



382 ELECTRO-DEPOSITION OF METALS. 

55. Nickel sulphate. — Beautiful dark green crystals, readily 
soluble in water, the solution exhibiting a green color. On heat- 
ing the crystals to above 536° F., yellow anhydrous nickel sul- 
phate remains behind. Like the double salt described below, it 
serves for the preparation of nickel baths and for coloring zinc. 

Recognition. — By compounding the solution with ammonia the 
green color passes into blue. Potassium carbonate precipitates 
pale green basic nickel carbonate, which dissolves on adding am- 
monia in excess, the solution showing a blue color. A content of 
copper is recognized by the separation of black-brown copper sul- 
phide on introducing sulphuretted hydrogen into the heated solu- 
tion previously strongly acidulated with hydrochloric acid. 

56. Nickel-ammonium sulphate. — It forms green crystals of a 
somewhat paler color than nickel sulphate. This salt dissolves 
with more difficulty than the preceding, 100 parts of water dis- 
solving only 5.5 parts of it. It is used for the same purposes as 
the nickel sulphate, and is also recognized in the same manner. 

57. Cobalt sulphate. — Crimson crystals of a sharp metallic taste, 
which are constant in the air and readily dissolve in water, the 
solution showing a red color. By heating, the crystals lose their 
water of crystallization without, however, melting, and become 
thereby transparent and rose-colored. The salt is used for cobalt 
baths for electro-cobalting and cobalting by contact. 

Recognition. — In the presence of ammoniacal salts, caustic pot- 
ash precipitates a blue basic salt, which, on heating, changes to a 
rose-colored hydrate, and by standing for some time in the air to 
a green-brown hydrate. By mixing a concentrated solution of 
the salt strongly acidulated with hydrochloric acid with solution 
of potassium nitrate, a reddish-yellow precipitate is formed. 

58. Cobalt-ammonium sulphate. — This salt forms crystals of the 
same color as cobalt sulphate, which, however, dissolve more 
readily in water. 

59. Sodium sulphite and bisulphite. — a. Sodium sulphite. Clear, 
colorless, and odorless crystals, which are rapidly transformed 
into an amorphous powder by efflorescence. The salt readily 
dissolves in water, the solution showing a slight alkaline reaction 
due to a small content of sodium carbonate. It is employed in 



PRODUCTS USED IN ELECTRO-PLATING. 383 

the preparation of gold, brass, and copper baths, for silvering by 
immersion, etc. 

Recognition. — The solution when mixed with dilute sulphuric 
acid has an odor of burning sulphur. 

b. Sodium bisulphite. Small crystals, or more frequently in the 
shape of a pale yellow powder with a strong odor of sulphurous 
acid and readily soluble in water. The solution shows a strong 
acid reaction and loses sulphurous acid in the air. It is employed 
in the preparation of alkaline copper and brass baths. 

Both the sulphite and bisulphite must be kept in well-closed 
receptacles, as by the absorption of atmospheric oxygen they are 
converted to sulphate. 

VIII. Nitrates. 

60. Potassium nitrate (saltpetre, nitre). — It forms large, prismatic 
crystals, generally hollow, but also occurs in commerce in the form 
of a coarse powder, soluble in 4 parts of water at a medium tem- 
perature. The solution has a bitter, saline taste and shows a 
neutral reaction. Potassium nitrate melts at a glowiug heat, and 
on cooling congeals to an opaque, crystalline mass. It is em- 
ployed in the preparation of desilvering baths and for producing 
a dead lustre upon gold and gilding. For these purposes it may, 
however, be replaced by the cheaper sodium nitrate, sometimes 
called cubic nitre or Chile saltpetre. 

Recognition. — A small piece of coal when thrown upon melt- 
ing saltpetre burns fiercely. When a not too dilute solution of 
saltpetre is compounded with solution of potassium bitartrate 
saturated at the ordinary temperature, a crystalline precipitate 
of tartar is formed. 

61. Sodium nitrate {cubic nitre or Chile saltpetre). — Colorless 
crystals, deliquescent and very soluble in water ; the solution 
shows a neutral reaction. It is used for the same purposes as 
potassium nitrate. 

62. Ilercurous nitrate. — It forms small, colorless crystals, which 
are quite transparent and slightly effloresce in the air. On 
heating they melt and are transformed, with the evolution of 
yellow-red vapors, into yellow-red mercuric oxide, which, on 



384 ELECTRO-DEPOSITION OF METALS. 

further heating, entirely evaporates. With a small quantity of 
water, mercurous nitrate yields a clear solution ; by the further 
addition of water it shows a milky turbidity, which, however, 
disappears on adding nitric acid. It is employed for quicking 
the zincs of the elements and the objects previous to silvering, 
and for brightening gilding. For the same purposes is also 
used : — 

63. Mercuric nitrate. — It is difficult to obtain this salt in a 
crystallized form. It is generally sold in the form of an oily, 
colorless liquid, which, in contact with water, separates a basic 
salt. This precipitate disappears upon the addition of a few 
drops of nitric acid, and the liquid becomes clear. 

Recognition. — A bright ribband of copper dipped in solution 
of mercurous or mercuric nitrate becomes coated with a white 
amalgam, which disappears upon heating. 

64. Silver nitrate (lunar caustic). — This salt is found in com- 
merce in three forms : either as crystallized nitrate of silver in 
thin, rhombic, and transparent plates; or in amorphous, opaque, 
and white plates of fused nitrate ; or in small cylinders of white, 
or grav or black color, according; to the nature of the mould em- 
ployed, in which form it constitutes the lunar caustic for surgical 
uses. For our purposes only the pure, crystallized product, free 
from acid, should be employed. The crystals dissolve readily in 
water. In making solutions of this and other silver salts, only 
distilled water should be used ; all other waters, owing to the ' 
presence of chlorine, produce a cloudiness or even a distinct pre- 
cipitate of silver chloride. In the heat the crystals melt to a color- 
less, oily fluid, which, on cooling, congeals to a crystalline mass. 
Silver nitrate is employed in the preparation of chloride and 
cyanide of silver for silver baths ; the solution in potassium 
cyanide may also be used for silver baths. The alcoholic solu- 
tion is employed for metallizing moulds. 

Recognition. — Hydrochloric acid and common salt solution pre- 
cipitate from silver nitrate solution silver chloride, which becomes 
black on exposure to the light, and is soluble in ammonia. 



PRODUCTS USED IN ELECTRO-PLATING. 385 

IX. Phosphates and Pyrophosphates. 

65. Sodium phosphate. — Large, clear crystals, which readily 
effloresce, and whose solution in water shows an alkaline reac- 
tion. It is employed in the preparation of gold baths and for 
the production of metallic phosphates for soldering. 

Recognition. — The dilute solution compounded with silver 
nitrate yields a yellow precipitate of silver phosphate. 

66. Sodium pyrophosphate. — It forms white crystals, which are 
not subject to efflorescence, and are soluble in 6 parts of water at 
a medium temperature; the solution shows an alkaline reaction. 
Sodium pyrophosphate also occurs in commerce in the form of an 
anhydrous white powder, though it may here be said that the 
directions for preparing baths refer to the crystallized salt. It is 
employed in the preparation of gold, nickel-bronze, and tin baths. 

Recognition. — The dilute solution compounded with silver 
nitrate yields a white instead of a yellow precipitate. 

67. Ammonium phosphate. — A colorless crystalline powder 
quite readily soluble in water; the solution should be as neutral 
as possible. A salt smelling of ammonia, as well as one showing 
an acid reaction, should be rejected. It is employed in the 
preparation of platinum baths. 

X. Salts of the Organic Acids. 

68. Potassium bitartrate (cream of tartar). — The pure salt forms 
small transparent crystals of an acid taste, and slightly soluble in 
water. The commercial crude tartar or argol, which is a by- 
product in the wine industry, forms gray or dirty red crystalline 
crusts. In a finely powdered state, purified tartar is called cream 
of tartar. It is employed for the preparation of the whitening 
silver baths, for those of tin, and for the silvering paste by 
friction. 

69. Potassium sodium tartrate (Rochelle or Seignette salt). — 
Clear colorless crystals, constant in the air, of a cooling bitter 
saline taste, and soluble in 2.5 parts of water of a medium tem- 
perature. The solution shows a neutral reaction. This salt is 

25 



386 ELECTRO-DEPOSITION OF METALS. 

employed in the preparation of copper baths free from cyanide, 
as well as of nickel and cobalt baths, which are to be decomposed 
in the single cell apparatus. 

Recognition. — By the addition of acetic acid the solution yields 
an abundant precipitate of tartar. 

70. Antimony-potassium tartrate (tartar emetic). — A white crys- 
talline substance, of which 100 parts of cold water dissolve 5 
parts, while a like volume of hot water dissolves 50 parts. The 
solution shows a slightly acid reaction. The only use of this salt 
is for the preparation of antimony baths. 

Recognition. — The solution compounded with sulphuric, nitric, 
or oxalic acid yields a white precipitate, insoluble in an excess of 
the cold acid. Sulphuretted hydrogen imparts to the dilute solu- 
tion a red color. Hydrochloric acid effects a precipitate, which 
is redissolved by the acid in excess. 

71. Copper acetate (verdigris). — It is found in the market in 
the form of dark green crystals showing an acid reaction, or of a 
neutral bright green powder. 

The crystallized copper acetate forms opaque dark green prisms, 
which readily effloresce, becoming thereby coated with a pale 
green powder ; they dissolve with difficulty in water, but readily 
in ammonia, forming a solution of a blue color, as well as in 
potassium cyanide and alkaline sulphites. 

The neutral copper acetate forms a blue-green crystalline pow- 
der, imperfectly soluble in water, but readily soluble in ammo- 
nia, forming a solution of a blue color. 

Copper acetate is used for preparing copper and brass baths, 
for the production of artificial patinas, for coloring, gilding, etc. 

72. Lead acetate (sugar of lead). — Colorless lustrous prisms or 
needles of a nauseous sweet taste and poisonous. The crystals 
effloresce in the air, melt at 104° F., and are readily soluble in 
water, yielding a slightly turbid solution. Lead acetate is em- 
ployed for preparing lead baths (jSTobili's rings) and for coloring 
copper and brass. 

Recognition. — By compounding lead acetate solution with potas- 
sium chromate solution, a heavy yellow precipitate of lead chro- 
mate is formed. 




PRODUCTS USED IN ELECTRO-PLATING. 387 

73. Sodium citrate. — Colorless crystals, presenting a moist ap- 
pearance, which are readily soluble in water; the solution should 
show a neutral reaction. This salt is employed in the preparation 
of the platinum bath according to Bottger's formula. 

B. Various Apparatus and Instruments. 

Glass balloons and flasks. — These are spheres of thin blown 
glass, Fig. 131, with necks of various dimensions in length and 
diameter. They are employed for heating acids, dis- 
solving metals, and a great many other uses. They 
should be placed upon triangular supports of iron and 
at a certain distance from the fire, from the direct 
action of which they are to be protected by the inter- 
vention of a piece of wire gauze or its equivalent. 
The thinner they are the more easily they bear sud- 
den changes of temperature. They are preferable to 
porcelain evaporating dishes for dissolving gold, be- 
cause there is much less danger of losing a part of the product 
by spurting. 

Evaporating dishes or capsules. — These are usually vessels of 
porcelain, and are intended to bear a high temperature. The 
best are thin and uniformly so. Like glass flasks, they should 
be supported above the fire upon an iron stand and wire gauze. 
As far as practicable they should be gradually heated and cooled. 
When taken from the fire they should be placed upon rings made 
of plaited straw. They are made with or without lips, and some 
have a socket for a wooden handle. Glass evaporating dishes are 
not durable. 

Glass jars. — These are glass vessels, generally cylindrical, closed 
at one end, and of different capacities. 

They are employed for small gilding, silvering, and electro- 
plating baths in the cold. They are handy and serviceable for 
amateurs, because their transparency permits the progress of the 
operation to be observed at all times. 

Crucibles. — These are vessels, the shape of which is generally 
an inverted truncated cone, Fig. 132, the smaller end being closed, 



ELECTEO-DEPOSITION OF METALS. 




Fig. 132. a nd the larger open. Sometimes the opening is tri- 
angular. 

Crucibles are made of many kinds of materials : 
metals, refractory clay, stoneware, porcelain, plumbago or 
graphite, etc. They are generally provided with a cover 
of the same material, and are raised above the grate 
bars of the furnace by means of bricks or cylinders of 
clay. Metallic crucibles may be heated rapidly, but the others 
require to have their temperature raised gradually and carefully. 
They are employed for the preparation of many salts, for the fusion 
of metals, etc. Non-metallic crucibles are rarely used for more 
than one operation. 

Hydrometers. — These are glass instruments resembling ther- 
mometers in outward appearance, but having a large bulb near 
the bottom. They are used for testing the specific gravity of 
liquids, or, in other words, to test their density as compared with 
that of pure water. The liquid to be tested may be placed in a 
narrow glass jar, Fig. 133, together with the hydrometer, or may 
be contained in any other vessel. The instru- 
ment floats in the liquid to be tested, with its 
bulb below the surface and its stem standing 
above the surface. This stem is graded into 
degrees similar to that of a thermometer, and 
shows the depth of the bulb beneath the sur- 
face. In pure water the bulb sinks down to the 
0° mark, or to 1.000 as marked on some scales, 
1.000 being taken to represent the density of 
water at a temperature of 60° F. As the den- 
sity of water increases by the addition of salts 
or of liquids having a greater density than water, 
the bulb is forced upwards, and the scale then reg- 
isters so many degrees greater density than water. 
Three differently graduated hydrometers are 
in use, viz., hydrometers graded to read direct 
the specific gravity of liquids in comparison with that of water, 
taking this as represented by 1.000; hydrometers graded by a 
scale adopted by Mr. "W. Twaddell, and known as Twaddell's 
hydrometers ; and hydrometers graded by a scale adopted by 



Fig. 133. 



«a 




PRODUCTS USED IN ELECTRO-PLATING. 



389 



M. Baume, and named Baume's hydrometers. The difference 
between the three gradings is shown in the following table : — 



Table showing 


readings of different hydrometers. 


Specific gravity. 


Baume. 


Twaddell. 


Specific gravity. 


Baume. 


Twaddell. 


.817° 


40° 


_ 


1.250° 




50° 


.827 


38 


— 


1.263 


30° 


— 


.837 


36 


— 


1.300 


— 


60 


.847 


34 


— 


1.321 


35 


— 


.856 


32 


— 


1.350 


— 


70 


.871 


30 


— 


1.385 


40 


— 


.880 


28 


— 


1.400 


— 


80 


.892 


26 


: 


1.450 


— 


90 


.903 


24 





1.454 


45 


— 


.915 


22 





1.500 


— 


100 


.928 


20 





1.532 


50 


— 


.942 


18 





1.550 


— 


110 


.955 


16 





1.600 


— 


120 


.970 


14 





1.618 


55 


— 


.985 


12 





1.650 


— 


130 


1.000 


0° or 10 


0° 


1.700 


— 


140 


1.036 


5 


— 


1.714 


60 


— 


1.050 


— 


10 


1.750 


— 


150 


1.075 


10 


— 


1.800 


— 


160 


1.100 


— 


20 


1.823 


65 


— . 


1.116 


15 


— 


1.850 


— 


170 


1.150 


— 


30 


1.900 


_ . 


180 


1.161 


20 


— 


1.946 


70 


— 


1.200 


— 


40 


1.950 


— 


190 


1.210 


25 


— 









It will be seen that every degree Twaddell represents 0.005° 
in the specific gravity hydrometer, and every 10° represents 
0.050°. To convert degrees Baume into readings showing direct 
specific gravity, subtract the readings on Baume's scale from the 
number 144, and divide this by the difference. For example, 

144 

144 — 66 = = 1.846°, the specific gravity of a liquid regis- 

78 

tering 66° on a Baume hydrometer. Baume has one hydrometer 
for liquids lighter than water (the readings of which arc given in 
the first 16 sets of figures in the foregoing table), and one for 
liquids heavier than water. 

Filters. — Filtering a solution, a bath, or any other liquor, con- 
sists in causing it to pass through a permeable substance, the pores 
or meshes of which are sufficiently close to retain all the undis- 
solved substances, which are thus separated from the liquid part. 



390 



ELECTRO-DEPOSITION OF METALS. 



Fig. 134. 




Fig. 135. 



Filters are of very different materials and shapes. Cloth, mus- 
lin, etc., are coarse filters or strainers, made in 
the form of pockets. Their filtering power is 
considerably improved by covering them with 
a layer of sand, wool, boneblack, etc. These 
latter substances themselves, properly supported, 
will act as filters. 

Felted wool (generally rabbit's hair) is made 

in the shape of a conical pocket (Fig. 134), but 

is suited only for neutral substances. Alkalies 

destroy it rapidly. 

Concentrated acids are filtered through amianthus, or asbestos, 

compressed in the neck of a glass funnel upon broken fragments 

of glass. 

The most useful filtering material, however, is unsized paper. 
This filter (Fig. 135) is prepared by folding diago- 
nally a square piece of porous paper, which thus 
prepared forms a triangle. This is again folded in 
half. Then, beginning at one edge, smaller folds 
are made alternately to the right and to the left, 
but all converging towards the point, like a fan. 
The filter is now partially opened, trimmed on top, 
and introduced into the funnel, care being had that all the pro- 
jecting edges rest against it. 

If it be feared that the filter will not resist the weight of the 
liquid, the point is twisted to the left or to the right, and while 
it is still held between two fingers of the left hand, the whole 
filter is inverted, so that the inward folds become 
the outward ones. A filter with such a rounded 
point is better supported in the funnel, and filters 
more rapidly. 

This method is preferable for rapid filtration ; but 
if it is desired to recover precipitates, the filter repre- 
sented by Fig. 136 is more suitable. A circular sheet of paper is 
twice doubled up, and by carefully opening it three thicknesses 
of paper are laid on one side, leaving one single thickness on the 
other side. 




Fig. 136. 




PRODUCTS USED IN ELECTRO-PLATING. 



391 



Siphons. — The most simple and handy siphon, in many cases, 
is a piece of lead pipe bent so as to have two unequal branches, 
the smaller of which plunges into the liquid to be drawn off. A 
section of India-rubber tube may be employed for similar pur- 
poses. 

But as these materials may be chemically acted upon by 
various solutions, glass siphons are used, with or without a suc- 
tion tube (Figs. 137 and 138). 



Fig. 137. 



Fig. 138. 





For siphoning corrosive solutions which cannot be touched 
with the fingers, a siphon with a suction tube is used (Fig. 137). 
The shorter leg is plunged into the liquid and the longer one 
closed with the finger or an India-rubber pad pressed against it ; 
then, with the mouth, suction should be carefully applied at the 
lateral suction tube until the liquid fills the longer leg. 

If there be any danger of inhaling a poisonous vapor, the 
action of the mouth may be replaced by an India-rubber ball 
fastened to the suction tube. The longer branch of the siphon 
is closed as before, and the ball compressed in order to remove 
the air. By its elasticity the ball resumes its former volume, thus 
producing a suction which starts the siphon in action. 

Stirring rods. — These are rods made of various materials, and 
are employed for mixing together liquids or pastes, or liquids and 



392 ELECTBO-DEPOSITION OF METALS. 

pastes, or solids with liquids, or various solids in the dry state. 
Their length and thickness should be suited to the volumes to 
be mixed. 

Suitable stirring rods are those which have no chemical action 
upon the substances with which they are brought in contact ; 
neither should they become impregnated with them. Rods of 
glass, stoneware, or porcelain are decidedly the best. Wood and 
most metals should be avoided, because the former is absorbent 
and the latter are corroded and easily oxidized. 

The operator should always have near at hand a complete 
assortment of glass stirrers of various sizes, and with fused or 
rounded ends, in order not to scratch the vessels in which he 
operates. 



USEFUL TABLES. 



393 



CHAPTER XVIII. 



USEFUL TABLES. 



Table of elements with their symbols, atomic weights, and 
specific gravities. 



N3,m6. 


Sym- 


Atomic 


Specific 




Sym- 


Atomic 


Specific 




bol. 


weight. 


gravity. 




bol. 


weight. 


gravity. 


Aluminium 


Al 


27.4 


2.67 


Molybdenum 


Mo 


96 


8.60 


Antimony . 




Sb 


122 


6.72 


Nickel . . 


Ni 


58 


8.8 


Arsenic 






As 


75 


5.63 


Niobium . . 


Nb 


94 


6.67 


Barium 






Ba 


137 


4.00 


Nitrogen . 


N 


14 


0.972 


Beryllium 






Be 


9.3 


2.10 


Osmium . 


Os 


199.4 


21.3 


Bismuth 






Bi 


208 


9.799 


Oxygen . . 


O 


16 


1.088 


Boron . 






B 


11 


2.68 


Palladium 


Pd 


106.6 


11.8 


Bromine 






Br 


80 


2.97 


Phosphorus . 


P 


31 


1.84 


Cadmium 






Cd 


112 


8.67 


Platinum . 


Pt 


197.4 


21.15 


Caesium 






Cs 


133 


— 


Potassium 


K 


39.1 


8.865 


Calcium 






Ca 


40 


3.10 


Rhodium . 


Rh 


104.4 


12.10 


Carbon 






C 


12 


3.50 


Rubidium 


Rb 


85.4 


1.50 


Cerium 






Ce 


92 


— 


Ruthenium . 


Ru 


104.4 


11.40 


Chlorine 






CI 


35.5 


2.45 


Selenium . 


Se 


79.4 


4.28 


Chromium 






Cr 


52 


6.81 


Silicium . 


Si 


28 


2.49 


Cobalt . 






Co 


58.8 . 


8.50 


Silver . 


Ag 


108 


10.50 


Copper . 






Cu 


63.4 


8.88 


Sodium 


Na 


23 


0.972 


Didymium 






D 


95 


— 


Strontium 


Sr 


87.5 


2.54 


Erbium 






E 


112.6 


— 


Sulphur . 


S 


32 


2.045 


Fluorine 






F 


19 


— 


Tantalum 


Ta 


182 


10.78 


Gold . 






Au 


197 


19.50 


Tellurium 


Te 


128 


6.18 


Hydrogen 






H 


1 


0.069 


Thallium . . 


IT 


204 


11.86 


Indium 






In 


75.6 


— 


Thorinum 


Th 


231 


7.70 


Iodine . 






I 


127 


4.98 


Tin . . . . 


Sn 


118 . 


7.29 


Iridium 






Ir 


197.4 


21.15 


Titanium 


Ti 


50 


5.30 


Iron 






Fe 


56 


7.70 


Tungsten 


W 


184 


19.10 


Lanthanun 


L 




La 


92 


— 


Uranium . 


U 


120 


18.40 


Lead 






Pb 


207 


11.38 


Vanadium 


V 


51.3 


5.50 


Lithium 






Li 


7 


0.59 


Yttrium . . 


Y 


68 





Magnesium 




Mg 


24 


1.74 


Zinc . . . 


Zn 


65 


6.86 


Manganese 




Mn 


55 


8.00 


Zirconium 


Zr 


89.6 


4.20 


Mercury 




Hg 


200 


13.59 











394 



ELECTRO-DEPOSITION OF METALS. 



Table < 


rf chemical and electro-chemical equivale 


nts. 


Name of substance. 


Symbol. 


Specific 
gravity. 


Chemical 
equiva- 
lent. 


Electro- 
chemical equi- 
valent. 
Milligrammes. 


Weights 
decomposed 
by 1 ampere 

in 1 hour. 

In grammes. 


Hydrogen . 


H 


1 


1 


0.01036 


0.0375 


Aluminium 






A\ 


2.6 


13.7 


0.14250 


0.5137 


Antimony . 






Sb 


6.8 


122 


1.26880 


4.5750 


Arsenic 








As 


5.7 


75 


0.78000 


2.8125 


Cobalt 








Co 


8.7 


29 5 


0.30680 


1.1062 


Copper 








Cu 


8.8 


31.8 


0.33070 


1.1925 


Gold . 








Au 


19.2 


98.3 


1.02230 


3.6862 


Iron . 








Fe 


7.5 


28 


0.29120 


1.0500 


Lead . 








Pb 


11.3 


103.5 


1.07640 


3.8812 


Nickel 








Ni 


8.6 


29.5 


0.30680 


1.1062 


Platinum 








Pt 


21.2 


98.6 


1.02540 


3.6975 


Silver 








Ag 


10.5 


108 


1.12320 


4.0500 


Tin . 








Sn 


7.3 


32.7 


0.34010 


1.2262 


Zinc • 








Zn 


7.2 


59 


0.61360 


2.2125 



With the assistance of this table it can be calculated how long 
a measured surface has to remain in the bath in order to acquire 
a deposit of determined weight with the most suitable current 
density. Suppose the time is to be determined which a square 
decimetre of surface has to remain in the nickel bath in order to 
acquire a deposit of y\j millimetre thick with a current density of 
0.5 ampere. First calculate the weight of the deposit by multi- 
plying the surface in square millimetres with the thickness and 
specific gravity. One square decimetre is equal to 30,000 square 
millimetres, which, multiplied by y 1 -^ millimetre, gives as a product 
1000, which, multiplied by the specific gravity of nickel — 8.6 — 
gives 8600 milligrammes = 8.6 grammes. Since, for the regular 
deposit per square decimetre, a current density of 0.5 ampere is 
required, and 1 ampere deposits, according to the above table, 
1.1062 grammes in 1 hour, \ ampere deposits 0.5331 gramme 
in 1 hour, and, therefore, about 16 hours will be required for the 
deposition of 8.6 grammes. 

According to this example, the time, for instance, can also be 
calculated which one, two, or more dozen of knives and forks or 
spoons, which are to have a deposit of silver of a determined weight, 
must remain in the bath when the current density is known. Sup- 
pose 50 grammes of silver are to be deposited upon 1 dozen of 



USEFUL TABLES. 



395 



spoons, and the most suitable current density is 0.2 ampere per 
square decimetre; if the surface of 1 spoon represents 1.10 square 
decimetres, the surface of 1 dozen spoons of equal size is 13.2 
square decimetres. Hence, they require 13.2 x 0.2 = 2.64 am- 
peres ; now, since 1 ampere deposits in one hour 4.05 grammes of 
silver, 2.64 amperes deposit in the same time 10.7 grammes of 
silver, and with this current the dozen spoons must remain about 
4f hours in the bath for the deposition of 50 grammes of silver 
upon this surface. 



Table showing the value of equal current volumes as expressed in 
amperes per square decimetre, per square foot, and per square 
inch of electrode surface. 



to * -S 

<b s a) 
u era 
to 5 w 
^o 
poo 


GO O) 

ii ftt " 


so O 
o u 

if =* 

tO ~< 

§■§* . 

I* 8 


o a o 

tO CO ° 

Jk'3 
a a> o 


= Amperes 
per square 
foot. 


to o 

O Sh 

a!- 

^ 03 rt 

II p^ 


,r, * is 

tO tO g 

g-n'3 

a o o 
4j e/o 


to O 

o u 

u CS 

eh 

^!§ 

ii ft! " 


on <D 

o u 

£§ 
&=* . 


0.05 


0.46 


0.0032 


0.8 


7.43 


0.0516 


6.20 


57.6 


0.4 


0.054 


0.5 


0.0035 


0.86 


8 


0.0555 


6.46 


60 


0.4167 


0.077 


0.72 


0.005 


0.9 


8.36 


0.0581 


7 


65.0 


4516 


0.1 


0.93 


0.0064 


0.93 


8.64 


0.06 


7.53 


70 


0.4861 


0.11 


1 


0.0069 


0.97 


9 


0.0625 


7.75 


72.0 


0.5 


0.15 


1.44 


0.01 


1 


9.29 


0.0645 


8 


74.3 


0.5161 


0.2 


1.86 


0.0129 


1.08 


10 


0.0694 


8.61 


80 


0.5555 


0.22 


2 


0.0139 


1.09 


10.08 


0.07 


9 


83.6 


0.5806 


0.3 


2.79 


0.0193 


1.24 


11.52 


0.08 


9.30 


86.4 


0.6 


0.31 


2.88 


0.02 


1.39 


12.96 


0.09 


9.69 


90 


0.6250 


0.32 


3 


0.0208 


1.55 


14.4 


0.1 


10 


92.9 


0.6452 


0.4 


3.71 


0.0258 


2 


18.6 


0.1290 


10.76 


100 


0.6944 


0.43 


4 


0.0278 


2.15 


20 


0.1389 


10.85 


100.8 


0.7 


0.46 


4.32 


0.03 


3 


27.9 


0.1935 


12.40 


115.2 


0.8 


0.5 


4.64 


0.0323 


3.10 


28.8 


0.2 


13.95 


129.6 


0.9 


0.54 


5 


0.0348 


3.23 


30 


2083 


15.50 


144.0 


1 


0.6 


5.57 


0387 


4 


37.1 


0.2581 


20 


185.8 


1.2903 


0.62 


5.76 


0.04 


4.30 


40 


0.2778 


21.53 


200 


1.3889 


0.65 


6 


0.0417 


4.60 


43.2 


0.3 


30 


278.7 


1.9355 


0.7 


6.50 


0.0452 


5 


46.4 


0.3226 


31.0 


288 


2 


0.75 


1 


0.0486 


5.38 


50 


0.3478 


32.3 


300 


2 0833 


0.77 


7.20 


0.05 


6 


55.7 


0.3871 


46.5 


432.0 


3 



By this table the current density may be expressed in amperes 
per square decimetre, square foot, or square inch, any of them 
being given. Thus a current of 1 ampere per square decimetre 
has the same electrolytic value as one of 9.29 amperes per square 
foot or 0.0645 per square inch. To find the value of intermediate 



396 



ELECTRO-DEPOSITION OF METALS. 



numbers, not shown above, add together the various numbers 
representing the hundreds, tens, units, and decimals of the given 
quantity. Thus 27.5 amperes per square decimetre ( = 20 + 7 + 5) 
are equivalent to 185.8 + 65 + 4.64 = 255.44 amperes per square 
foot, or 1.2903 + 0.4516 + 0.0323 = 1.7742 amperes per square 
inch. 

Table showing the specific electrical resistances* of different 
sulphuric acid solutions atva?'ious temperatures (Fleeming 
Jenlcin). 



Specific 


Temperatures (Fahrenheit). 


gravity of 
acid. 


32° 


39.2° 


46.4° 


53.6° 


60.8° 


68° 


75.2° 


82 4° 


].10 


1.37 


1.17 


1.04 


0.92 


0.84 


0.79 


0.74 


0.71 


1.20 


1.33 


1.11 


0.93 


0.79 


0.67 


0.57 


0.49 


0.41 


1.25 


1.31 


1.09 


0.90 


0.74 


0.62 


0.51 


0.43 


0.36 


1.30 


1.36 


1.13 


0.94 


0.79 


0.66 


0.56 


0.47 


0.39 


1.40 


1.69 


1.47 


1.30 


1.16 


1.05 


0.96 


0.89 


0.84 


1.50 


2.74 


2.41 


2.13 


1.89 


1.72 


1.61 


1.32 


1.43 


1.60 


4.32 


4.16 


3.62 


3.11 


2.75 


2.46 


2.21 


2.02 


1.70 


9.41 


7.67 


6.25 


5.12 


4.23 


3,57 


3.07 


2.71 



Table showing the specific electrical resistances* of different copper 
sulphate solutions at various temperatures (Fleeming Jenkin). 



No. of parts of 






Temperatures (Fahrenheit). 






copper sulphate 














dissolved in 100 
















parts of water. 


57.2° 


60.8° 


64.4° 


68° 


75.2° 


82.4° 


86° 


8 


45.7 


43.7 


41.9 


40.2 


37.1 


34.2 


32.9 


12 


36.3 


34.9 


33.5 


32.2 


29.9 


27.9 


27.0 


16 


31.2 


30.0 


28.9 


27.9 


26 1 


24.6 


24.0 


20 


28.5 


27.5 


26.5 


25.6 


24.1 


22.7 


22.2 


24 


26.9 


25.9 


24.8 


23.9 


22.2 


20.7 


20.0 


28 


24.7 


23.4 


22.1 


21.0 


18.8 


16.9 


16.0 



* By the term " specific resistance," in the above tables, is meant the abso- 
lute resistance in ohms of a column of the liquid 1 square centimetre in cross- 
section and 1 centimetre long ; in other words, it is the resistance of a cubic 
centimetre of the liquid. The diminution of resistance accompanying a rise 
of temperature should be especially marked. 



USEFUL TABLES. 



397 



Table of the electro-motive force of elements. 



Name of element. 


Constitution. 


Electro- 
motive force 
in volts. 


Authority. 


Wollaston . .. 


Amalgamated zinc and cop- 
per in dilate sulphuric 
acid (1 : 12). 


f 0.886 
\ 0.861 
I 0.719 


Clark and Sabine. 

Sprague. 

De la Rive. 


Smee 


Amalgamated zinc in sul- 
phuric acid ; platinized 
silver, or platinum in sul- 
phuric acid (1 : 12). 


f 1.098 
J 1.107 
1 0.541 
[ 1.192 


Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 


Daniell 


Amalgamated zinc in sul- 
phuric acid (1 : 4) ; cop- 
per in saturated solution 
of copper sulphate. 


f 1.079 
do. 
do. 

L do. 


Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 


do. . . . 


Zinc in dilute sulphuric acid 
(1 : 12) ; copper as above. 


/ 0.978 
\ 0.98 


Clark and Sabine. 
Du Moncel. 


Leclanche . 


Zinc in sal ammoniac, carbon 
with manganese peroxide 
in sal ammoniac. 


f 1.481 
J 1.561 
1 1.942 
[ 1.259 


Clark and Sabine. 
Sprague. 
De la Rive. 
Beetz. 


do. . . . 


Zinc in solution of common 
salt ; carbon with manga- 
nese peroxide in common 
salt solution. 


f 1.493 
\ 1.360 
[ 1.34 


Sprague. 
Naclari. 
Du Moncel. 


Marie Davy 


Zinc in dilute sulphuric acid 
(1 : 12) ; carbon in mercu- 
rous sulphate. 


f 1.524 
J 1.542 
| 1.482 
[ 1.440 


Clark and Sabine. 
Sprague. 
Naclari. 
Du Moncel. 


Grove . 


Zinc in dilute sulphuric acid 
(1 : 12) ; platinum in fum- 
ing nitric acid. 


1.956 


Clark and Sabine. 


do. . . . 


Zinc as above ; platinum in 
nitric acid of 1.38 sp. gr. 


f 1.524 
\ 1.542 


Clark and Sabine. 
Sprague. 


Bnnsen . . . 


Zinc as above ; carbon in 
fuming nitric acid. 


/ 1.964 
\ 1.95 


Clark and Sabine. 
Du Moncel. 


do. . . . 


Zinc as above ; carbon in 
nitric acid of 1.38 sp. gr. 


f 1.888 
\ 1.941 
[ 1.880 


Clark and Sabine. 

Beetz. 

Naclari. 


do. . . . 


Zinc as above ; carbon in bi- 
chromate of potassium. 


f 2.028 
\ 1.905 
(. 2.120 


Clark and Sabine. 

Sprague. 

Naclari. 


Grenet . . . 


Zinc and carbon in bichro- 
mate of potassium. 


1.825 


Naclari. 



398 



ELECTRO-DEPOSITION OF METALS. 



Table showing the solubility of various substances. 





in water 










in alcohol of 


Substances of which 1 part is soluble 






59° F. 




of 59° F. 


of 212° F. 




Alum ..... 


6.5 


0.3 


insoluble. 


Ammonium carbonate 


4.0 


decomposes 


soluble. 


Citric acid .... 


0.75 


0.6 


soluble. 


Copper sulphate (blue vitriol) 


5.0 


1.3 


insoluble. 


Ferric chloride 


0.6 


very soluble 


soluble. 


Ferrous chloride 


8 


a 


soluble. 


Ferrous sulphate (green vitriol) 


1.5 


0.3 


insoluble. 


Iodine ..... 


7000 


soluble 


readily • 
soluble. 


Nickel nitrate .... 


2.0 


very soluble 


soluble. 


" sulphate 


3.0 


2.0 


insoluble. 


Potash ..... 


09 


very soluble 


insoluble. 


" caustic 


0.5 


(< 


soluble. 


Potassium cyanide . 


readily 


readily 


soluble. 




soluble 


soluble 




" dichromate (red chro- 








mate of potash) . 


10 


1.2 


insoluble. 


Sal ammoniac .... 


3.0 


1.4 


sparingly 
soluble. 


Silver, citrate .... 


sparingly 


sparingly 







soluble 


soluble 




" nitrate . • . 


0.8 


very soluble 


1 part at a 
boiling heat. 


Soda ..... 


1.0 


0.3 


insoluble. 


" caustic .... 


2.0 


0.5 


insoluble. 


Sodium bisulphite . 


soluble 


soluble 





" chloride 


2.8 


2.5 


60 


" sulphite 


4.0 


1.0 


insoluble. 


Yellow prussiate of potash 


4.0 


1.0 


insoluble. 


Zinc chloride .... 


0.3 


very soluble 


1 


" sulphate .... 


2.0 


1.0 


insoluble. 



Table Showing the Composition of the Host Usual Alloys and 

Solders. 

Alloys are combinations or mixtures, effected by the fusion of 
two or more different metals in definite proportions. The electro- 
plater employs them so constantly that it is important that he be 
acquainted with the compositions of the most usual alloys, and 
that he learn the preparation of several of them, which, like the 
fusible alloys of Darcet, will often be serviceable. 

It is, of course, possible to vary ad infinitum the mixtures and 
the proportions of the component metals given in the following 



USEFUL TABLES. 



399 



table, and thus to arrive at an unlimited number of alloys which, 
on account of slight differences of color, ductility, sonorousness, 
etc., have received a great variety of names.* 

1. Alloys. 



Argentan, elastic . 
Brass for articles worked with 
the hammer 

" for turning . 

" for decorating purposes 

" for sheet 

Britannia 

u 

Bronze for bells 

" for larger bells . 

" for smaller bells 

" for clocks 

" for cymbals 

" for gongs 

" for medals . 

" for large ordnance 

" for small ordnance 

" for statues . 



Chrysochalk . 
Darcet's fusible alloy 



German silver 



Potin (French yellow brass) 
Similor .... 
Talmi gold . 
Telescope mirrors (reflectors) 
Tombac .... 

" pale . . 

" red . 

" resembling gold 













t»» 







































"3 


3 


B 


a 


a 


d 


t3 

OS 


J4 

o 


ti 


h 


N 


H 


h! 


£ 


M 


< 


< 



57.4 

70 

66 

60 

75 
4 

10 

80 

78 

42, 

75 

80 
100 
100 

90 

93 

84 

84 

82 

80 



50 
53 
8 
4 
55 
11. 

100 
86. 

100 
80 
76 
88 
84 



Pakts. 



25 

30 

32 

40 
25 



11 

10.5 



3.5 

31.25 

3.5 

1 

17 
24.9 
12 
12.6 

20 
24 
12 
16 



70.5 

22 

20 

22 

58 

25 

20 

25 

8 

10 

7 

16 

4 

18 

8 

4 

3 

2 



2 
1.2 



2.4 
50 



0.2 



1.2 



13 



4 

15.75 

3 

1 

23 



— 25.5 

— 62 



* For a full description of alloys and amalgams see " The Metallic Alloys," 
edited by W. T. Brannt. Philadelphia . Henry Carey Baird & Co. 1889. 



400 



ELECTRO-DEPOSITION OF METALS. 



2. Solders. 
a. Soft Solder. 



Tin. 


Lead. 


Melts 
at degrees F. 


Tin. 


Lead. 


Melts 


Parts. 


Parts. 


at degrees F. 


1 
1 
1 
1 
1 
1 


25 
]0 
5 
3 
2 
1 


558° 

541 

511 

482 

441 

370 


H 

2 
3 
4 
5 
6 


1 
1 
1 
1 
1 
1 


334° 
340 
356 
365 

378 
381 



b. Hard Solder. 













Brass. 


Zinc. 


Tin. 




Parts. 


Very refractory . 


85.42 


12.58 





it (t 










7 


1 


— 


Refractory 










3 
4 


1 
1 


— 


Readily fusible 










5 
5 


2 
4 


— 


Half wbite 










12 


5 


1 


(i 










44 


20 


2 


Wbite 










40 


2 


8 


it 










22 


2 


4 


<< 










18 


12 


30 


Very ductile 










78.25 


17.25 


— 



c. Silver Solder. 





Silver. 


Copper. 


Brass. 1 Tin. 


Zinc. 




Parts. 


Brass silver solder 

Hard silver solder 

Very bard solder 

Middling bard solder . 

Soft silver solder .... 

Silver solder for cast iron 

Silver solder for steel . 


1 
4 
40 
40 
32 
20 
30 


1 
10 
10 

30 
10 


1 

40 
32 


10 

2 


10 



USEFUL TABLES. 

d. (lold Solder. 



401 



Hard solder for fineness 750 
Soft " " " 750 

Solder for fineness 583 
583 
" " " less than 583 



Solder readily fusible 



for yellow gold 



Gold. 



Copper. 



Zinc. 



9 


2 


1 


12 


7 


3 


3 


2 


1 


2 


0.5 


0.5 


1 


2 


1 


1 


2 


— 


1 


— 


2 


11.94 


54.74 


28.17 


10 


5 


— 



5.01 
1 



Table of the melting-points of some metals. 



Metals. 


Degrees, 
Fahrenheit. 


Metals. 


Degrees, 
Fahrenheit. 


Tin .... 
Lead .... 
Zinc .... 
Antimony . ' . 
Brass 
Copper 


458.6 
599.4 
773.6 
809.6 

1859 

1994 


Gold .... 

Iron, crude 

Nickel 

Steel 

Iron, bar . 


2372 

2912 to 3092 

2912 

3092 to 3452 

3452 to 3812 



Table of high temperatures. 




Description. 


Degrees, 
Fahrenheit. 


Description. 


Degrees, 
Fahrenheit. 


Incipient red heat 

A red heat 

A dull red heat visible 

in daylight 
Heat < f a common fire 
A full red heat . 
Dull red heat 


977 
980 

1000 
1140 
1200 
1310 


An orange-red heat . 
A bright red heat 
A dull white heat 
A white heat 
Heat of a good blast 
furnace . 


1700 
1873 
1996 
3000 

3300 



Table of the specific gravity and content of solutions of potassium 
carbonate at 57.2° Fahrenheit, according to Gerlach. 



Potassium 




Potassium 




Potassium 




carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


per cent. 




per cent. 




per cent. 




2 


1.01829 


20 


1.19286 


38 


1.39476 


4 


1.03658 


22 


1.21402 


40 


1.41870 


6 


1.05513 


24 


1.23517 


42 


1.4433S 


8 


1.07396 


26 


1.25681 


44 


1.46307 


10 


1.09278 


28 


1.27893 


. 46 


1.49314 


12 


1.11238 


30 


1.30105 


48 


1.51861 


14 


1.13199 


32 


1.32417 


50 


1.54408 


16 


1.15200 


34 


1.34729. 


52 


1.57048 


18 


1.17243 


36 


1.37082 


52.024 


1.57079 



26 



402 



ELECTRO-DEPOSITION OF METALS. 



Table showing the specific gravity of sulphuric acid at 59° F., 
according to Kolb. 



a 3 
9> « 


Specific 
gravity. 


100 parts by 
weight 
contain 


One litre 
contains in 
kilogrammes 


<3 
A 


Specific 
gravity. 


100 parts by 
weight 
contain 


One litre 
contains in 
kilogrammes 




so 3 


HoS0 4 . 


S0 3 . 


H 2 S0 4 . 


so 3 . 


H 2 S0 4 . 


so 3 . 


H 2 S0 4 . 





1.000 


0.7 


0.9 


0.007 


0.009 


34 


1.308 


32.8 


40.2 


0.429 


0.526 


1 


1.007 


1.5 


1.9 


0.015 


0.019 


35 


1.320 


33.8 


41.6 


0.447 


0.549 


2 


1.014 


2.3 


2.8 


0.023 


0.028 


36 


1.332 


35.1 


43.0 


0.468 


0.573 


3 


1.022 


3.1 


3.8 


0.032 


0.039 


37 


1.345 


36.2 


44.4 


0.487 


0.597 


4 


1.029 


3.9 


4.8 


0.040 


0.049 


38 


1.357 


37.2 


45.5 


0.505 


0.617 


5 


1.037 


4.7 


5.8 


0.049 


0.060 


39 


1.370 


38.3 


46.9 


0.525 


0.642 


6 


1.045 


5.6 


6.8 


0.059 


0.071 


40 


1.383 


39.5 


48.3 


0.546 


0.668 


7 


1.052 


6.4 


7.8 


0.067 


0.082 


41- 


1.397 


40.7 


49.8 


0.569 


0.696 


8 


1.060 


7.2 


8.8 


0.076 


0.093 


42 


1.410 


41.8 


51.2 


0.589 


0.722 


9 


1.067 


8.0 


9.8 


0.085 


0.105 


43 


1 424 


42.9 


52.8 


0.611 


0.749 


10 


1.075 


8.8 


10.8 


0.095 


0.116 


44 


1.438 


44.1 


54.0 


0.634 


0.777 


11 


1.083 


9.7 


11.9 


0.105 


0.129 


45 


1.453 


45.2 


55.4 


0.657 


0.805 


12 


1.091 


10.6 


13.0 


0.116 


0.142 


46 


1.468 


46.4 


56.9 


0.681 


0.835 


13 


1.100 


11.5 


14.1 


0.126 


0.155 


47 


1.483 


47.6 


58.3 


0.706 


0.864 


14 


1.108 


12.4 


15.2 


0.137 


0.168 


48 


1.498 


48.7 


59.6 


0.730 


0.893 


15 


1.116 


13.2 


16.2 


0.147 


0.181 


49 


1.514 


49.8 


61.0 


0.754 


0.923 


16 


1.125 


14.1 


17.3 


0.159 


0.195 


50 


1.530 


51.0 


62.5 


0.780 


0.956 


17 


1.134 


15.1 


18.5 


0.172 


0.210 


51 


1.540 


52.2 


64.0 


0.807 


0.990 


18 


1.142 


16.0 


19.6 


0.183 


0.224 


52 


1.563 


53.5 


65.5 


0.836 


1.024 


19 


1.152 


17.0 


20.8 


0.196 


0.233 


53 


1.580 


54.9 


67.0 


0.867 


1.059 


20 


1.162 


18.0 


22.2 


0.209 


0.258 


54 


1.597 


56.0 


68.6 


0.894 


1.095 


21 


1.171 


19.0 


23.3 


0.222 


0.273 


55 


1.615 


57.1 


70.0 


0.922 


1.131 


22 


1.180 


20.0 


24.5 


0.236 


0.289 


56 


1.634 


58.4 


71.6 


0.954 


1.170 


23 


1.190 


21.1 


25.8 


0.251 


0.307 


57 


1.652 


59.7 


73.2 


0.986 


1.210 


24 


1.200 


22.1 


27.1 


0.265 


0.325 


58 


1.672 


61.0 


74.7 


1.019 


1.248 


25 


1.210 


23.2 


28.4 


0.281 


0.344 


59 


1.691 


624 


76.4 


1.055 


1.292 


26 


1.220 


24.2 


29.6 


0.295 


0.361 


60 


1.711 


63.8 


78.1 


1.092 


1.336 


27 


1.231 


25.3 


31.0 


0.311 


0.382 


61 


1.732 


65.2 


79.0 


1 129 


1.384 


28 


1.241 


26.3 


32.2 


0.326 


0.400 


62 


1.753 


66.7 


81.7 


1.169 


1.432 


29 


1.252 


27.3 


33.4 


342 


0.418 


63 


1.774 


68.7 


84.1 


1.219 


1.492 


30 


1.263 


28.3 


34.7 


0.357 


0.438 


64 


1.796 


70.6 


86.5 


1.268 


1.554 


31 


1.274 


29.4 


36.0 


0.374 


0.459 


65 


1.819 


73.2 


89.7 


1.332 


1.632 


32 


1.285 


30.5 


37.4 


0.392 


0.481 


66 


1.842 


81.6 


100.0 


1.503 


1.842 


33 


1.297 


31.7 


38.8 


0.411 


0.503 















USEFUL TABLES. 



403 



Table of the specific gravity and content of nitric acid, 
according to Kolb. 



m"3 


Specific 
gravity. 


100 parts 

contain at 

32° F. 


100 parts 

contain at 

59° F. 


VV 

ft 


Specific 
gravity. 


100 parts 

contain at 

32° F. 


100 parts 

contain at 

59° F. 


p 


HN0 3 . 


N 2 6 . 


HNO3. 


N0O5. 


HNO3. 


N 2 5 . 


HNO s . 


N 2 5 . 





1.000 


0.0 


0.0 


0.2 


0.1 


28 


1.242 


36.2 


31.0 


38.6 


33.1 


1 


1.007 


1.1 


0.9 


1.5 


1.3 


29 


1.252 


37.7 


32.3 


40.2 


34 5 


2 


1.014 


2.2 


1.9 


2.6 


2.2 


30 


1.261 


39.1 


33.5 


41.5 


35.6 


3 


1.022 


3.4 


2.9 


4.0 


3.4 


31 


1.275 


41.1 


35.2 


43.5 


37.3 


4 


1.029 


4.5 


3.9 


5.1 


4.4 


32 


1.286 


42.6 


36.5 


45.0 


38.6 


5 


1.036 


5.5 


4.7 


63 


5.4 


33 


1.298 


44.4 


38.0 


47.1 


40.4 


6 


1.044 


6.7 


5.7 


7.6 


6.5 


34 


1.309 


46.1 


39.5 


48.6 


41.7 


7 


1.052 


8.0 


6.9 


9.0 


7.7 


35 


1.321 


48.0 


41.1 


50.7 


43.5 


8 


1.060 


9.2 


7.9 


10.2 


8.7 


36 


1.334 


50.0 


42.9 


52.9 


45.3 


9 


1.067 


10.2 


8.7 


11.4 


9.8 


37 


1.346 


51.9 


44.5 


55.0 


47.1 


10 


1.075 


11.4 


9.8 


12.7 


10.9 


38 


1.359 


54.0 


46.3 


57.3 


49.1 


11 


1.083 


12.6 


10.8 


14.0 


12.0 


39 


1.372 


56.2 


48.2 


59.6 


51.1 


12 


1.091 


13.8 


11.8 


15.3 


13.1 


40 


1.384 


58.4 


50.0 


61.7 


52.9 


13 


1.100 


15.2 


13.0 


16.8 


14.4 


41 


1.398 


60.8 


52.1 


64.5 


55.3 


14 


1.108 


16.4 


14.0 


18.0 


15.4 


42 


1.412 


63.2 


54.2 


67.5 


57.9 


15 


1.116 


17.6 


15.1 


19.4 


16.6 


43 


1.4 '6 


66.2 


56.7 


70.6 


60.5 


16 


1.125 


18.9 


16.2 


20.8 


17.8 


44 


1.440 


69.0 


59.1 


74.4 


63.8 


17 


1.134 


20.2 


17.3 


22.2 


19.0 


45 


1.454 


72.2 


61.9 


78.4 


67.2 


18 


1.143 


21.6 


18.5 


23.6 


20.2 


46 


1.470 


76.1 


65.2 


83.0 


71.1 


19 


1.152 


22.9 


19.6 


24.9 


21.3 


47 


1.485 


80.2 


68.7 


87.1 


74.7 


20 


1.161 


24.2 


20.7 


26.3 


22.5 


48 


1.501 


84.5 


72.4 


92.6 


79.4 


21 


1.171 


25.7 


22.0 


27.8 


23.8 


49 


1.516 


88.4 


75.8 


96.0 


82.3 


22 


1.180 


27.0 


23.1 


29.2 


25.0 


49.5 


1.524 


90.5 


77.6 


98.0 


84.6 


23 


1.190 


28.5 


24.4 


30.7 


26.3 


49.9 


1.530 


92.2 


79.0 


100.0 


85.71 


24 


1.199 


29.8 


25.5 


32.1 


27.5 


50.0 


1.532 


92.7 


79.5 


— 


— 


25 


1.210 


31.4 


26.9 


33.8 


289 


50 5 


1.541 


95.0 


81.4 


— 


— 


26 


1.221 


33.1 


28.4 


35.5 


30.4 


51.0 


1.549 


97.3 


83.4 


— 


— 


27 


1.231 


34.6 


29.7 


37.0 


31.7 


51.5 


1.559 


100.0 


85.71 


— 


— 



Table showing the specific gravity of sal ammoniac solutions at 
66.2° F., according to Schif. 



Content of 

the solution, 

per cent. 


Specific 
gravity. 


Content of 

the solution, 

per cent. 


Specific 
gravity. 


Content of 

the solution, 

per cent. 


Specific 
gravity. 


1 


1.0029 


11 


1.0322 


21 


1.0606 


2 


1.0058 


12 


1.0351 


22 


1.0633 


3 


1.0087 


13 


1.0380 


23 


1.0660 


4 


1.0116 


14 


1.0409 


24 


1.0687 


5 


1.0145 


15 


1.0438 


25 


1.0714 


6 


1.0174 


16 


1.0467 


26 ' 


1.0741 


7 


1.0203 


17 


1.0495 


27 


1.0768 


8 


1.0233 


18 


• 1.0523 


28 


1.0794 


9 


1.0263 


19 


1.0551 


29 


1.0820 


10 


1.0293 


20 


1.0579 


30 


1.0846 



404 



ELECTRO-DEPOSITION OF METALS. 



Table showing the electrical resistance of pure copper wire 
of various diameters. 







Number of 






Number of 


No. of wire, 
Birmingham 
wire gauge. 


Resistance of 
1 foot in ohms. 


feet required 

to give 

resistance 

of 1 ohm. 


No. of wire, 
Birmingham 
wire gauge. 


Resistance of 
1 foot in ohms. 


feet required 

to give 

resistance 

of 1 ohm. 


0000 


0.0000516 


19358 


17 


0.00316 


316.1 


000 


O.O0U05S9 


16964 


18 


0.00443 


225.5 


00 


0.0000737 


13562 


19 


0.00603 


165.7 





0.0000922 


10857 


20 


0.00869 


115.1 


1 


0.000118 


8452.6 


21 


0.01040 


96.2 


2 


0.000132 


7575.1 


22 


0.01358 


73.6 


3 


0.000159 


6300.1 


23 


0.01703 


58.7 


4 


0.000188 


5319.9 


24 


0.02200 


45.5 


5 


0.000220 


4545.9 


25 


0.02661 


37.6 


6 


0.000258 


3870.3 


26 


0.03286 


30.4 


7 


0.000329 


3043.4 


27 


0.04159 


24.0 


8 


0.000391 


2557.1 


28 


0.05432 


18.4 


9 


0.000486 


2057.7 


29 


0.06300 


15.9 


10 


0.000593 


1686.5 


30 


0.07393 


13.5 


11 


0.000739 


1352.5 


31 


0.10646 


9.4 


12 


0.000896 


1116.0 


32 


0.13144 


7.6 


13 


0.001180 


847.7 


33 


0.16634 


6.0 


14 


0.001546 


647.0 


34 


0.21727 


4.6 


15 


0.002053 


4S7.0 


35 


0.42583 


2.4 


16 


0.002520 


396.8 


36 


0.66537 


1.5 



Beaistance and conductivity of pure copper at different 
temperatures. 



Centigrade 
temperature. 


Resistance. 


Conductivity. 


Centigrade 
temperature. 


Resistance. 


Conductivity. 


0° 


1.00000 


1.00000 


16° 


1.06168 


.94190 


1 


1.00381 


.99624 


17 


1.06563 


.93S41 


2 


1.00756 


.99250 


18 


1.06959 


.93494 


3 


1.01135 


.9SS78 


19 


1.07356 


.93148 


4 


1.01515 


.98508 


20 


1.07742 


.92814 


5 


1.01896 


.98139 


21 


1.08164 


.92452 


6 


1.02280 


.97771 


22 


1.08553 


.92121 


7 


1.02663 


.97406 


23 


1.08954 


.91782 


8 


1.03048 


.97042 


24 


1.09365 


.91445 


9 


1.03435 


.96679 


25 


1.09763 


.91110 


10 


1.03822 


.96319 


26 


1.10161 


.90776 


11 


1.04199 


.95970 


27 


1.10567 


.90443 


12 


1.04599 


.95603 


28 


1.11972 


.90113 


13 


1.04990 


.95247 


29 


1.11382 


.89784 


14 


1.05406 


.94893 


30 


1.11782 


.89457 


15 


1.05774 


.94541 









USEFUL TABLES. 



405 



Table showing actual diameters in decimal parts of an inch 
corresponding to the numbers of various wire gauges. 



No. of wire 


Eoebliug. 


Brown & 


Birmingham 


English legal 


Old English 


gauge. 


Sharpe. 


or Stubs. 


standard. 


or London. 


000000 


.46 


_ 




.464 




uoooo 


.43 


— 


— 


.432 


— 


0000 


.393 


.46 


.454 


.4 


.454 


000 


.362 


.40964 


.425 


.372 


.425 


00 


.331 


.3648 


.380 


.348 


.38 





.307 


.32495 


.340 


.324 


.34 


1 


.283 


.2893 


.3 


.3 


.3 


2 


.263 


.25763 


.284 


.276 


.284 


3 


.244 


.22942 


.259 


.252 


.259 


4 


.225 


.20431 


.238 


.232 


.238 


5 


.207 


.18194 


.22 


.212 


.22 


6 


.192 


.16202 


.203 


.192 


^203 


7 


.177 


.14428 


.IS 


.176 


.18 


8 


.162 


.12849 


.165 


.16 


.165 


9 


.148 


.11443 


.148 


.144 


.148 


10 


.135 


.10189 


.134 


.128 


.134 


11 


.120 


.09074 


.12 


.116 


.12 


32 


.105 


.08081 


.109 


.104 


.109 


13 


.092 


.07196 


.095 


.092 


.095 


14 


.08 


.06408 


.083 


.08 


.083 


15 


.072 


.05706 


.072 


.072 


.072 


16 


.063 


.05082 


.065 


.064 


.065 


17 


.054 


.04525 


.058 


.056 


.058 


18 


.047 


.0403 


.049 


.048 


.049 


19 


.041 


.03589 


.042 


.04 


.04 


20 


.035 


.03196 


.035 


.036 


.035 


21 


.032 


.02846 


.032 


.032 


.0315 


22 


.028 


.02534 


.028 


.028 


.0295 


23 


.025 


.02257 


.025 


.024 


.027 


24 


.023 


.0201 


.022 


.022 


.025 


25 


.02 


.0179 


.02 


.02 


.023 


26 


.018 


.01594 


.018 


.018 


.0205 


27 


.017 


.01419 


.016 


.0164 


.01875 


28 


.016 


.01264 


.014 


.0148 


.0165 


29 


.015 


.01125 


.013 


.0136 


.0155 


30 


.014 


.01002 


.012 


.0124 


.01375 


31 


.0135 


.00893 


.010 


.0116 


.01225 


32 


.013 


.00795 


.009 


.0108 


.01125 


33 


.011 


.00708 


.008 


.01 


.01025 


34 


.01 


.0063 


.007 


.0092 . 


.0095 


35 


.0095 


.00561 


.005 


.0084 


.009 


36 


.009 


.005 


.004 


.0076 


.0075 



406 



ELECTRO-DEPOSITION OF METALS. 



Weight of iron, copper, and brass wire and plates. 
(Diameters and thickness determined by American gauge ) 







Weight of wire per 1000 


Weight of 


PLATES PER 


No. of 


Size of 


LINEAL 


FEET. 




SQUARE FOOT. 




gauge. 


each 

No. 


Wro't 
iron. 


Steel. 


Copper. 


Brass. 


Wro't 
iron. 


Steel. 


Copper. 


Brass. 




Inch. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


0000 

000 

00 




.46000 
.40964 
.36480 
.32486 


560.74 
444.68 
352.66 
279.67 


566.03 
448.88 
355.99 
282.30 


640.51 
507.95 
402.83 
319.45 


605.18 
479.91 
380.67 
301.82 


17.25 
15.3615 
13.68 
12.1823 


17.48 
15.5663 
13.8624 
12.3447 


20.838 
18.557 
16.525 
14.716 


19.688 
17.533 
15.613 
13.904 


1 

2 
3 
4 
5 


.28930 
.25763 
.22942 
.20431 
.18194 


221.79 
175.89 
139.48 
110.62 
87.720 


223.89 
177.55 
140.80 
111.66 

88.548 


253.34 
200.91 
159.32 
126.35 
100.20 


239.35 

189.82 
150.52 
119.38 
94.666 


10.8488 
9.6611 
8.6033 
7.6616 
6.8228 


10.9934 
9.7899 
8.7180 
7.7638 
6.9137 


13.105 
11.671 
10.393 
9.2552 
8.2419 


12.382 
11.027 

9.8192 
8.7445 
7.7«7 


6 

7 
8 
9 
10 


.16202 
.14428 
.12849 
.11443 
.10189 


69.565 
55.165 
43.751 
34.699 
27.512 


70.221 

55.685 
44.164 
35.026 
27.772 


79.462 
63.013 
49.976 
39.636 
31.426 


75.075 
59.545 
47.219 
37.437 
29.687 


6.0758 
5.4105 
4.8184 
4.2911 
3.8209 


6.1568 
5.4826 
4.8826 
4.3483 
3.8718 


7.3395 
6.5359 
5.8206 
5.1837 
4.6156 


6.9345 
6.1752 
5.4994 
4.8976 
4.3609 


11 
12 
13 
14 

15 


.090742 
.080808 
.071961 
.064084 
.057068 


21.820 
17.304 
13.722 
10.886 
8.631 


22.026 
17.468 
13.851 
10.989 
8.712 


24.924 
19.766 
15.674 
12.435 
9.859 


23.549 
18.676 
14.809 
11.746 
9.315 


3.4028 
3.0303 
2.6985 
2.4032 
2.1401 


3.4482 
3.0707 
2.7345 
2.4352 
2.1686 


4.1106 
3.6606 
3.2598 
2.9030 
2.5852 


3.8838 
3.4586 
3.0799 
2.742S 
2.4425 


16 
17 
18 
19 
20 


.050820 
.045257 
.040303 
.035890 
.031961 


6.845 
5.427 
4.304 
3.413 
2.708 


6.909 
5.478 
4.344 
3.445 
2.734 


7.819 
6.199 
4.916 
3.899 
3.094 


' 7.587 
5.857 
4.645 
3.684 
2.920 


1.9058 
1.6971 
1.5114 
1.3459 
1.1985 


1.9312 
1.7198 
1.5315 
1.3638 
1.2145 


2.3021 
2.0501 
4.8257 
1.6258 
1.4478 


2.1751 

1.937 

1.725 

1.5361 

1.3679 


21 
22 
23 

24 
25 


.028462 
.025347 
.022571 
.020100 
.017900 


2.147 
1.703 
1.350 
1.071 
0.8491 


2.167 
1.719 
1.363 
1.081 
0.8571 


2.452 
1.945 
1.542 
1.223 
.9699 


2.317 

1.838 
1.457 
1.155 
0.9163 


1.0673 
.95051 
.84641 
.75375 
.67125 


1.0816 
.96319 
.8577 
.7638 
.6802 


1.2893 
1.1482 
1.0225 
.91053 
.81087 


1.2182 
1.0849 
.96604 
.86028 
.76612 


26 
27 
28 
29 
30 


.015941 
.014195 
.012641 
.011257 
.010025 


0.6734 
0.5340 
0.4235 
0.3358 
0.2663 


0.6797 
0.5391 
0.4275 
0.3389 
0.2688 


.7692 
.6099 
.4837 
.3835 
.3042 


0.7267 
0.5763 
0.4570 
0.3624 

0.2874 


.59775 
.53231 
.47404 
.42214 
.37594 


.60572 
.53941 
.48036 
.42777 
.38095 


.72208 
.64303 
.57264 
.50994 
.45413 


.68223 
.60755 
.54103 
.48180 
.42907 


31 
32 
33 
34 
35 


.008928 
.007950 
.007080 
.006304 
.005614 


0.2113 
0.1675 
0.1328 
0.1053 
0.08366 


0.2132 
0.1691 
0.1341 
0.1063 
0.08445 


.2413 
.1913 
.1517 
.1204 
.0956 


0.2280 
0.1808 
0.1434 
0.1137 
0.9015 


.3348 
.29813 
2655 
.2364 
.21053 


.33926 

.3021 

.26904 

.23955 

.21333 


.40444 
.36014 
.32072 
.28557 
.25431 


.38212 
.34026 
.30302 
.26981 
.24028 


36 

37 
38 
39 
40 


.005000 
.004453 
.003965 
.003531 
.003144 


.06625 
.05255 
.04166 
.03305 
.02620 


.06687 
.05304 
.04205 
.03336 
.02644 


.0757 

.06003 

.04758 

.03755 

.02992 


.0715 

.05671 
.04496 
.03566 
.02827 


.1875 

.16699 

.14869 

.13241 

.1179 


.19 

.16921 

.15067 

.13418 

.11947 


.2265 

.20172 

.17961 

.15995 

.14242 


.2140 

.19059 

.16973 

.1511 

.13456 


Speci! 


ic grav. 


7.7747 


7.847 


8.880 


8.386 


7.200 


7.296 


8.698 


8.218 


Weigl 
cu 


Die foot 


185.874 


90.45 


554.988 


524.16 


450. 


456. 


543.6 


513.6 



USEFUL TABLES. 407 

Mules for Speed. 

To find speed of counter-shaft in accordance with main shaft and 
machine. — Subtract the number of revolutions of the main shaft 
from the number of revolutions the machine should make; divide 
the remainder by two. The quotient will show the number of 
revolutions of the countershaft. 

Example. — The main shaft runs 200 revolutions per minute, 
while the machine should run 1000 revolutions per minute. De- 
duct 200 from 1000, leaving 800, which divide by 2; the quo- 
tient will then be 400, which is the number of revolutions the 
countershaft should make. 

To find diameter of pulley on the main shaft. — Multiply the 
diameter in inches of the receiving pulley of the countershaft by 
the number of revolutions the countershaft should make and divide 
the product by the number of revolutions the main shaft makes. 

Example. — The countershaft makes 400 revolutions, the receiv- 
ing pulley is 7 J inches in diameter and the main shaft makes 200 re- 
volutions ; 400 times 7J equals 3000, which divided by 200 equals 
15: this is the diameter in inches of the pulley on the main shaft. 

To find diameter of pulley on countershaft carrying belt to 
machine. — Multiply the number of revolutions the machine 
should make by the diameter of pulley of the machine and 
divide by the number of revolutions the countershaft makes. 

Example. — Say the machine should make 1000 revolutions, 
the diameter of pulley on machine being 6 inches, and the counter- 
shaft making 400 revolutions; then multiplying 1000 by 6 equals 
6000 : dividing this by 400 gives 15, which should be the diame- 
ter of the pulley carrying belt from countershaft to machine, 

To find the speed of a machine. — Multiply the number of 
revolutions of the main shaft by the diameter of pulley in inches, 
and divide by the diameter of receiving pulley of the countershaft. 
The result is the speed of the countershaft. Then multiply the 
number of revolutions of countershaft by diameter of transmitting 
pulley, and divide by diameter of pulley on machine. The result 
will be the speed of the machine. It should be well understood 
that no other pulleys but those in contact with one belt should be 
considered. 



408 ELECTEO-DEPOSITION OF METALS. 

Comparison of the Scales of the Fahrenheit, Centigrade, and 
Reaumur Thermometers, and Rules for Converting one Scale 
into another. 

These three thermometers are graduated so that the range of 
temperature between the freezing and boiling points of water is 
divided by Fahrenheit's scale into 180 (from 32° to 212°), by 
the centigrade into 100 (from 0° to 100°), and by that of Reau- 
mur into 80 (from 0° to 80°) portions or degrees. 

The spaces occupied by a degree of each scale are consequently 
as |-, |-, and £ respectively, or as 1, 1.8, and 2.25 ; and the num- 
ber of degrees denoting the same temperature, by the three scales, 
when reduced to a common point of departure by subtracting 32 
from Fahrenheit's are as 9, 5, and 4. Hence, we derive the fol- 
lowing equivalents : — 

A degree of Fahrenheit's is equal to 0.5 of the centigrade or to 
0.4 of Reaumur's; a degree of centigrade is equal to 1.8 of 
Fahrenheit's or to 0.8 of Reaumur's; and a degree of Reaumur's 
is equal to 2.25 of Fahrenheit's, or to 1.25 of the centigrade. 

To convert degrees of Fahrenheit into the centigrade or Reau- 
mur's, subtract 32 and multiply the remainder by f- for the centi- 
grade or ^ for Reaumur's. 

To convert degrees of the centigrade or Reaumur's into Fahren- 
heit's, multiply the centigrade by •§-, or Reaumur's by £ ) as the 
case may be, and add 32 to the product. 



IND £X. 



ACCUMULATORS, 325 
Acid, arsenious, 367, 368 

arsenious ; addition of, to brass 

baths, 205 
boric, 367 

addition of, to nickel 

baths, 146 
nickel baths containing, 
149-151 
chromic, 368 
citric, 367 

free, determination of, in gal- 
vanoplastic baths, 313, 314 
hydrochloric, 366 
hydrocyanic, 366, 367 
hydrosulphuric, 369, 370 
muriatic, 366 
neutralization of, 126 
nitric, 366 

table of the specific 
gravity and content of, 
403 
potassium carbonate, 378 
prussic, 366, 367 
regaining of, from exhausted 

dipping baths, 130, 131 
sulphuric^ 365, 366 

table, showing the specific 
gravity of, at 59° F., 
402 
sulphydric, 369, 370 
Acids, 365-368 

carboy stand for, 134 
organic, salts of the, 385-387 
Action, local, 26 
Alkalies and alkaline earths, 368, 369 

poisoning by, 364 
Alkaline earths and alkalies* 368, 369 
Alliance machine, the, 6 
Alligator leather, plates for the pro- 
duction of imitations of, 343 
Alloy containing nickel, deposition of 
an, 186, 187 



Alloy- 

metallic, reduction of a, from the 
solution of its salts, 1 
Alloys and solders, table showing the 
composition of the most usual, 
398-401 
brush for scouring, 187 
metallic, deposition of, 6 
metallic, for the preparation of 

moulds, 335 
metallic, moulding in, 335 
nickel, deposits of, 187, 188 
table of, 399 
Alternating current machine, 54 

currents, 22 
Aluminium baths, 300, 301 
deposition of, 299-301 
-potassium sulphate, 380 
properties of, 299, 300 
Amalgamation of the zinc of elements, 

30, 31 
American giant dynamo, improved, 
of the Zucker & Levett Chemi- 
cal Co., 68-70 
polishing lathes, 117 
Ammeter or amperemeter, 95 
Ammonia, 369 
Ammonium-alum, 380 
chloride, 371 
hydrate, 369 
phosphate, 385 
sulphate, 380 
sulphide, 3 70 
Amreremeter or ammeter, 95 
Ampere, the, 28 
theory of, 10 
Anions, 24 
Anode, 24 

and object wires, coupling the, 
with the resistance-boards, volt- 
meter, shunt and baths, de- 
scription and illustrations of, 
98-101 



410 



INDEX. 



Anode — 

rods, cleansing of, 140 

wire, 87 
Anodes, arrangement of, 90, 91 

choice of, 140 

for brassing, 206, 207 

insoluble, 140, 153 

nickel, 153-156 

reddish tinge of, 156 

platinum, for gilding, 251, 252 

silver, 215-221 

suspension of, 91, 92 

used in galvanoplasty, 313 
Antimony baths, 297, 298 

chloride explosive power of de- 
posits of, 297 

deposition of, 297, 298 

deposits of, by contact, 299 

execution of deposits of, 299 

lustrous non-explosive deposit of, 
297, 298 

-potassium tartrate, 386 

properties of, 297 

sulphide, 370, 371 

trichloride, 372 
Apparatus and instruments, various, 

387-392 
Aqua fortis, 366 
Argentiferous pastes, composition of, 

237 
Armature, 52 

Brush, 58, 59 

Gramme, 54-56 

Siemens' s, 53 
Arsenic, 367, 368 

baths, 298, 299 

deposition of, 298, 299 

deposits of, by contact, 299 

execution of deposits of, 299 

poisoning by, 363, 364 

properties of, 298 

trisulphide, 371 
Arsenious acid, 36 7, 368 

addition of, to brass baths, 
205 

chloride, 372 

sulphide, 371 
Asphalt floors, 74 
Astatic galvanometer, 20 
Atoms, 24 
Auric chloride, 374 



BACCO'S copper bath, 201 
Backing metal, 327 
Baking powder, 378 



Balance, plating, 225, 226 
Balloons, glass, 387 
Baskets, dipping, 143 
Bath, bright-dipping, 127,235 

conditions required to guarantee 

good performance of a, 141 
copper, for the cell-apparatus, 307 
for galvanoplastic operations with 

gold, 347 
for galvanoplastic operations with 

silver, 347 
neutrality of a, 146, 147 
nickelling, acid reaction of the, 

145, 146 
nickelling, additions to the, 145, 

146 
suspending the objects in the, 160 

161 
working the, with the electric 
current, 139 
Baths, aluminium, 300, 301 

and batteries, rooms for the, 72, 

73 
antimony, 297, 298 
arsenic, 298, 299 
boiling of, 138, 139 
brass,"203-209 
bronze, 211, 212 
concentration of, 136, 137 
constant agitation of, 138 
copper, 192-198 

for galvanoplastic depositions 
with a separate source of 
current, 310 
exhausted dipping, regaining acid 

and metal from, 130, 131 
fdtration of, 139, 140 
for silvering by immersion, 232- 

237 
galvanoplastic, contrivances for 
the motion of, 312, 313 
current densities for, 311 
determination of free acid 
in, 313. 314 
of the content of copper 
in, 314, 315 
general rules for the preparation 

of, 134 
gold, 247-251 

heating of, 252, 253 
management of, 251-253 
preparation of, with the as- 
sistance of the current, 
251 
heating of, 73 

the room containing the, 73 



INDEX. 



411 



Baths- 
illustrations of coupling elements 

for different, 76, 77 
importance of the purity of the 

chemicals used for, 135, 136 
iron, management of, 296 
lead, 292 
light and ventilation of the room 

containing the, 72, 73 
nickel, 144-152 

preparation of, 144-147 
old, recovery of nickel from, 184 
palladium, 281 
removal of dust from, 140 
resistance-boards, voltmeter and 
shunt, coupling the, with the 
object and anode wires, de- 
scription and illustrations of, 
98-101 
securing lasting qualities to, 140 
silver, 213-215 

current-strength for, 215, 

216 
recovery of silver from old, 

245, 246 
treatment of, 215-221 
steel, 293, 294 
stirring of, 137 
temperature of, 138 
tin, 282-285 

management of, 285 
vats for heating, 89 
water for, 134, 135 
zinc, 289, 290 
Batteries and baths, rooms for the, 
72, 73 
plunge or bichromate, 42-44 
Battery, bichromate, Fein's, 43 

bichromate, Reiser & Schmidt's, 

43 
copper bath for the galvanoplastic 

depositions with the, 310 
galvanoplastic depositions with 

the, 309 
plunge, Bunsen, 42, 43 
reduction of metals without a, 

141-143 
Stoehrer's, 45 
trough, 2, 29 
Baume's hydrometers, 389 
Beardslee, G. W., cobalt solution 

recommended by, 1 90 
Becquerel, element of, 32 
Bell metal, composition of, 203 
Belt strapping attachment, 119, 120 



Benzine, removing oily or greasy 

matter with, 131, 132 
Bertrand's aluminium bath, 300 

palladium bath, 281 
Bicarbonate of potash, 378 
Bichromate batteries, 42-44 
battery, Fein's, 43 

Keiser & Schmidt's, 43 
element, 44, 45 
Bicycle-power plating dynamo of the 
Hanson & Van Winkle Co., of 
Newark, N. J., 68 
Bird, Dr., production of the amal- 
gams of potassium and sodium by, 4 
Black-lead, gilt or silvered, 321 
Black-leading, brushes used for, 108 
discovery of, 5 
machine, 319 
moulds, 319-321 
Black sulphide of antimony, 370 
Blue vitriol, 381 

pure crystallized, table of the 
content of, 307 
Bob, polishing, to impregnate the, 

with polishing material, 120, 121 
Bobs, 116 

Boettger, Prof., observations of, on 
the deposition of nickel, 5, 6 
platinum bath of, 275, 276 
Boiling pans, 138, 139 
Book plates, mounting of, 328 
Boric acid, 367 

addition of, to nickel baths, 

146 
nickel baths containing, 149- 
151 
Bouant's process of amalgamating the 

zinc of elements, 30, 31 
Brandley's directions for preparing 

gelatine moulds, 341 
Brass and bronzes, coloring of, 351- 
354 
articles, small, tinning solution 

for, 287 
baths, 203-209 

formation of slime on the 

anodes in, 207 
fresh, working of, 204, 205 
black deposit on, 299 
bronze and copper, deposition of, 

192-212 
bronze Barbedienne on, 352, 353 
brown color on, 352, 353 
castings, grinding of, 116 
color resembling gold on, 352 



412 



INDEX. 



Brass — 

composition of, 203 
deadening of, by pickling, 128 
deposits, polishing of, 124 

scratch-brushes for, 122 
gray color with a bluish tint on, 

352 
lustrous black on, 351 
nickel bath for, 151 
objects, bath for tinning, 282 
pickling of, 127 
potassium cyanide as a pickle 

for, 127, 128 
preparation of, for silvering, 222 
production of, by the galvanic 

method, 291, 292 
red, composition of, 203 
removing oxide from, 1 33 
sheets, grinding of, 116 
silvering small articles of, 236, 

237 
steel-gray on, 351, 352 
straw color, to brown, through 

golden-yellow, and tombac 

color on, 352 
various colors on, 350, 351 
violet and corn-flower blue on, 

353 
wire and plates, table of the 

weight of, 406 
yellow, composition of, 203 
zi ncking of, 291 
Brassed articles, inlaying of, 211 
Brassing, 203-211 

anodes used in, 206, 207 

by contact and dipping, 210, 

211 
color of, 206 
execution of, 209, 210 
iron, 205, 206, 208 
zinc, 208 
Bright-dipping bath, 127, 235 
Bright Platinum Plating Co., plati- 
num bath patented by the, 276 
Britannia metal, preparation of, for 

plating, 230 
removing oxide from, 133 
silvering of, 228, 229 
Bronze Bartedienne on brass, 352, 

353 
baths, 211, 212 
brass and copper, deposition of, 

192-212 
dead-yellow or clay yellow to 

dark brown on, 353 
pickling of, 127 



Bronze — 

removing oxide from, 133 

zincking of, 291 
Bronzes and brass, coloring of, 351- 
354 

composition of, 203 
Bronzing, 211, 212 
Brugnatelli, discovery of electro-gild- 
ing by, 3 
Brush armature, 58, 59 

dynamo-machine, 58-60 
Brush-coppering, 201, 202 
Brushes, 107, 108 

circular scratch, 106, 107 

collecting, 52 

fibre, 115 

for frosting or satin finish, 105 
Buffs, cloth, construction of, 169 
Bunsen, elements of, 34, 35 
closet for, 73 
manipulation of, 38, 39 

improved cell, 35, 36 

plunge battery, 42, 43 
Burning or over-nickelling, 148, 158 
Burnishers, 125 
Burnishing, operation of, 124, 125, 

227, 228 
Busts, galvanoplastic reproduction of, 
333-338 

section of, for moulding, 334 
Butter of antimony, 372 

of zinc, 372, 373 



(1ALCIUM carbonate, 378, 379 
J hydrate, 369 
Capsule, porcelain, 264 
Capsules, 387 
Carbonates, 377-379 
Carbon disulphide as an addition to 
silver baths, 221 
or bisulphide, 370 
Carboy stand, 134 
Carlisle and Nicholson, decomposition 

of water by, 2 
Cast iron, brassing of, 208 

bronzing solution for, 211 
objects, pickling of, 126 
zinc bath for, 289, 290 
Castings, brass, grinding of, 116 
copper, grinding of, 116 
unground iron, brassing of, 210 
zinc, nickel bath for, 151 
treatment of, 116 
Cathode, 24 
Cations, 24 



INDEX. 



413 



Caustic potash, 368, 369 

soda, 369 
Cell-apparatus, construction of, 303- 
305 
copper bath for the, 307 
French form of, 305, 306 
galvanoplastic deposition in 
German form of, 306, 307 
the, 303-308 
Bunsen improved, 35, 36 
Cellulose lacquers and varnishes, 358, 

359 
Cement floors, 74 

Centimetre-gramme-second system, 27 
Centigrade thermometer, comparison 

of the scale of, 408 
Chain, galvanic, 14 
Chalk, 378, '379 
Chaperon and Lallande element, 39, 

40 
Chemical and electro-chemical equiv- 
alents, table of, 394, 395 
products and various apparatus 
and instruments used in 
electro-plating, 365-392 
used in electro-plating, 365- 
387 
Chemicals, importance of the purity 
of, 135, 136 
poisoning by, and the antidotes, 
363, 364 
Chile saltpetre, 383 
Chloride of gold solution, preparation 

of, 263-265 
Chlorine combinations, 371-374 

poisoning by, 364 
Christoflie & Co., replacement of 
batteries by magneto-electrical ma- 
chines by, 6 
Chromic acid, 368 
Circuit, closing the, 14 
Citric acid, 367 
Clamond's thermo-electric pile, 47, 

48 
Clarke and Saxton, electric gener- 
ators constructed by, 53 
Clausius's theory of molecules, 24, 25 
Clay, metallization of, 344 
Cleansing apparatus, 92, 93 
Cliches, nickelling of, 182-184 
Cloth buff's, construction of, 169 
Coal gas, heat units produced by one 

cubic meter of, 50 
Cobalt-ammonium sulphate, 382 

and nickel, deposition of, 143- 
191 



Cobalt- 
baths, 189 
carbonate, 379 
chloride, 373 
properties of, 188 
sulphate, 382 
Cobalting, 188-191 
by contact, 191 
Colcothar, 120 
Collecting brushes, 52 
Coloring, patinizing, oxidizing, etc., 

of metals, 347-361 
Colors, iridescent, production of, 4 
Commutator, 52 
cylinder, 52 
Conducting salts, 145 

wire, determination of the posi- 
tion of the magnetic needle to 
the, 19 
wires, calculating the thickness 
of, for dynamo machines, 103 
Conductor, resistance of a, 15 
Conductors, good and bad, 1 1 
Continuous current machine, 54 
Copper acetate, 386 

alloys, density of current for 
nickelling, 159 
silvering articles of, without 
the use of a current, 235, 
236 
articles, gilding of, 254 

silvered, stripping of, 243 
small, tinning solution for, 
287 
bath for the cell-apparatus, 307 
baths, 192-198 

for galvanoplastic deposi- 
tions with a separate 
source of current, 310. 
without potassium cyanide, 
196 
black color on, 349 
blue-black color on, 349 
blue-gray color on, 349 
brass and bronze, deposition of, 

192-212 
brown color on, 348 
carbonate, 379 
castings, grinding of, 116 
chloride, 372 
coating grasses, leaves, flowers, 

etc., with, 343 
coating laces and tissues with, 342 
coating wood with a galvano- 
plastic deposit of, 344 
coloring of, 34 7-351 



414 



INDEX. 



Copper — 

cyanides, 376 

dead-black color on, 349 

density of current for nickelling, 
159 

deposits, polishing of, 124 
scratch-brushes for, 1 22 

determination of the content of, 
in galvano-plastic baths, 314, 
315 

experiments on, by Smee and 
von Hubl, 302 

for galvanoplastic purposes, 301, 
302 

gilded, stripping of, 273 

massive, various colors on, 350, 
351 

nickel bath for, 151 

nickel salts for nickelling, 145 

objects, bath for tinning, 282 

pale-red to dark chestnut-brown 
on, 347, 348 

penetration of the deposit of, into 
the basis-metal, 200 

pickling of, 127 

plates, cobalted, experiments in 
stripping, 189, 190 

precipitated by electrolysis, pro- 
perties of, 301, 302 

preparation of, for silvering, 222 

printing - plates, galvanoplastic 
bath for, 3 1 
steeling of, 294, 295 

properties of, 192 

pure, table of the resistance and 
conductivity of, 404 

red-brown color on, 348, 349 

removing oxide from, 133 

salts, poisoning by, 363 

sheets, grinding of, 116 

silvering small articles of, 236, 
237 

steel-gray color on, 350 

sulphate, 381 

sulphate solutions, table showing 
the specific electrical resist- 
ances of different, 396 

wire and plates, table of the 
weight of, 40G 
fine, silvering of, 240 
pure, table showing the elec- 
trical resistance of, 404 

-zinc alloy serving as anode, solu- 
tion for the transfer of any, 
208, 209 
Corvin's niello, 342, 343 



Coulomb, law of, 11, 13 

the, 28 
Counter-current, 25, 161, 162 
Countershaft carrying belt to machine, 
to find diameter of pulley on, 
407 
to find the speed of, in accord- 
ance with main shaft and ma- 
chine, 407 
Couple, thermo-electric, 46 
Coupling, mixed, 18 

the object and anode wires with 
the resistance - boards, volt- 
meter, shunt, and baths ; de- 
scription and illustrations of, 
98-101 
Coppered art castings, inlaying of 
depressions of, 202, 203 
objects, coating of, with another 
metal, 200 
Coppering, 192-203 

anodes for, 194, 198 
by contact and dipping, 201 
execution of, 198-200' 
formation of stains in, 199 
preparation of articles for, 1 98 
small articles en masse, 200 
zinc, 201 
Cream of tartar, 385 
Crucibles, 387, 388 
Cruikshank, electro-depositions of 
metals noticed by, 3 
trough battery devised by, 2 
Cubic nitre, 383 
Cuiere furiti, 349 
Cuicre-pnli deposit, 203-211 
Cupric sulphate, 381 
Current, calculating the weight of the 
deposit of silver from the den- 
sity of the, 226 
counter or polarizing, 25, 161, 

162 
electrical, chemical actions of the, 

23-28 
electric, effects of the, 19 

working the bath with the, 
139 
galvanic, 14 

laws and actions of the, 14 
hydro-electric, 14 
primary or inductive, 22 
quantity of, 15-19 

coupling elements for, 18 
regulator, 79 
secondary or induced, 22 
sources of, 29-71 



INDEX. 



415 



Current-volumes, table showing the 
value of equal, as expressed iro 
amperes, 395, 396 
Currents, alternating, 22 

extra, 22 
Cyanides, 375-377 
poisoning by, 363 



DANTELL element of, 32 
Daub, R., cobalt bath recom- 
mended by, 190, 191 
Davy, Sir H., discovery of potassium 

and sodium by, 3 
Dead dip, 128 

Deposit, backing the, 326, 237 
cuivre poll, 203-211 
detaching the, from the mould, 
326 
Deposition, galvanoplastic, in the cell- 
apparatus, 303-308 
of antimony, arsenic, aluminium, 

297-301 
of copper, brass, and bronze, 

192-201 
of gold, 246-275 
of nickel and cobalt, 143-191 
of platinum and palladium, 275- 

281 
of silver, 212-246 
of tin, zinc, lead, and iron 282- 
296 
Depositions, galvanoplastic, by the 
battery and dynamo- 
machine, 308-313 
current-strength for, 324 
with dynamo- machines, 
309-313 
Dip, dead, 128 
Dipping baskets, 143 

baths, exhausted, regaining acid 

and metal from, 130, 131 
or pickling, 93 
Doctor, the, 184 

Drinking-cups, gilding the inner sur- 
face of, 255 
Du Fresne's method of gilding, 272 
Duns's potash element, 40, 41 
Dupre, A., solution for filling Bun- 
sen elements proposed by, 37 
Dynamo- and magneto-electric ma- 
chines, 51-71 
bicycle-power plating, of the 
Hanson & Van Winkle Co., 68 
electric machine, constituent parts 
of a, 52 



Dynamo-electric machine — 

definition of a, 52 
first application of the term, 52 
generator, constituent parts of a, 

52 
improved American giant, of the 
Zucker & Levett Chemical Co., 
of New York, 68-70 
machine, best, for galvanoplastic 
depositions, 309 
Brush, 58-60 

copper bath for galvano- 
plastic depositions with 
the, 310 
Fein's, 58 
Gramme's, 8, 54-57 
Hefner- Alteneck's, 8 
Kroettlinger, 62 
Eahmeyer, 62-64 
location of the resistance- 
board of the, 95 
new, of the Hanson & Van 
Winkle Co., of Newark, 
N. J., 65-68 
Schuckert's, 8, 57. 58 
Siemens and Halske, 8, 61 
transition of the electro- 
magnetic machine to the, 
53, 54 
Weston's, 8, 64, 65 
machines, 54 

arrangements with, 93-103 
calculating the thickness of 
conducting wires for, 103 
impulse in the art of electro- 
plating due to, 70 
rules for setting up and run- 
ning, 93, 94 
various, 8, 70 
Dyne, 27 



EBERMAYER, Dr., experiments 
of, in coloring brass, 353, 
354 
silver bath for immersion, accord- 
ing to, 234, 235 
Electric connection gripper, 322 
current, effects of the, 19 
generators, constructed by Sax- 
ton and Clarke, 53 
division of, 54 
induction, discovery of, 4 
units, 27, 28 
Electrical machine, Pixii's, 53 
potential, 14 



416 



INDEX. 



Electrical — 

science, basis of the recent im- 
portant developments of, 51 
Electricity, 11-19 

and magnetism, 9-28 
contact, discovery of, 1 
creation of a current of, 13 
discovery of a new source of, 46 
double fluid, hypothesis of, 12, 13 
kinds of, 1 2 
resinous or negative, 12 
single fluid, hypothesis of, 13 
thermo-, 46 
vitreous or positive, 12 
Electro-chemical and chemical equiv- 
alents,- table of, 394, 395 
equivalents, 26, 27 
processes, investigators and 
practitioners of, 8 
-deposit, penetration of the, into 

the basis-metal, 140, 141 
-deposited metals, porosity of, 

121 
-deposition by contact, 141, 143 
imitation of niel by, 242 
processes of, 134, 143 
-etching, 330-332 
-gilder, brush used by the, 107 
-gilding, discovery of, 3 
-magnet, definition of a, 11 
-magnetic induction machine, 

first, 4 
-magnetism, 19-21 
-magnets, 20, 21 

-metallurgy, historical review 
of, 1-8 
origin of the term, 5 
-motive force, 14, 15 

coupling elements for, 

18 
of elements, table of, 

397 
or tension, series of, 13, 
14 
-nickelling, process of, 156-162 
-plated objects, finished, treat- 
ment of, 123, 124 
•plating arrangements in particu- 
lar, 76-103 
chemical products and va- 
rious apparatus and instru- 
ments used in, 365-392 
chemical products used in, 

365-387 
establishment, ground-plan 
of a, 101-103 



Electro-plating — 

establishments, arrangement 

of, in general, 72-103 
mechanical treatment of me- 
tallic articles before, 104, 
121 
mechanical treatment of me- 
tallic articles during and 
after, 121-126 
plant, constituent parts of a, 

76 
processes, rules for, 160, 161 
-silvering, ordinary, bath for, 214, 
215 
Electrochromy, 293 
Electrodes, 24 
Electrolysis, 23-28 

consumption of power in, 27 
development of, 1 
properties of copper precipitated 
by, 301, 302 
Electrolyte, 23 
Electrolytic law, Faraday's, 4 

laws, Faraday's, 25, 26 
Electropoion, composition of, 36 
Electroscope, the, 11, 12 
Electrotypes in iron, baths for, 294 

nickelling of, 182-184 
Element, Becquerel's, 32 
bichromate, 44, 45 
Daniell's, 32 
Dun's potash, 40, 41 
galvanic, 14 
Grove's, 33, 34 

Lallande and Chaperon, 39, 40 
. Leclanche, 39 
Meidinger, 33 

new, patented in Germany, 41, 42 
Smee's, 31, 32 
Elements, amalgamation of the zinc 
of, 30, 31 
Bunsen, closet for, 73 

manipulation of, 38, 39 
Bunsen's, 34, 35 
choice of coupling, 76, 77 
constant, 32 
coupling of, 17-19 

for electro-motive force or 

tension, 18 
for quantity of current, 18 
electro-plating arrangement with, 

76-93 
galvanic, 29-46 

illustrations of coupling, for dif- 
ferent baths, 76, 77 
location of, 37 



INDEX. 



417 



Elements — 

table of the electromotive force 
of, 397 
with their symbols, atomic 
weights, and specific gravi- 
ties, 393 
various, 40 

■with one fluid, reasons for the 
decrease of current in, 30, 31 
Elkingtons establishment, contrivance 
in the, for keeping the articles 
in the silver bath in gentle mo- 
tion, 220 
progress in the galvanoplastic art 
due to the, 5 
Eisner, bronze bath according to, 211 

tinning bath of, 287 
Emery, kinds of, used in grinding, 

112 
Equivalents, electro-chemical, 26, 27 
Essential resistance, 1 6 
Etching, electro, 330-332 

ground, compositions for, 331, 
332 
Evaporating dishes, 387 
External resistance, 1 G 
Extra currents, 22 

Eyes and hooks, silvering of, 236, 237 
coppering of, 202 
tinning of, 287 



FAHRENHEIT'S thermometer, 
comparison of the scale of, 408 
Farad, the, 28 
Faraday, discovery by, 51 

of electric induction by, 
4 
the chemical action of 
the current by, 23 
electrolytic law of, 4 
laws of, 25, 26 
Fein, dynamo-machine of, 58 
Fein's bichromate battery, 43 
Ferric oxide, 120 
sulphide, 371 
Ferrous sulphate, 380, 381 
Fibre brushes, 115 
Fibres, 115 
Field, magnetic, 11, 51 

maejnets, 52 
Filtersr389, 390 
Fire gilders, brush used by the, 107 

or mercury gilding, 269-271 
Flasks, glass, 387 
Floor of the working-room, 74 
27 



Flowers, coating of, with copper, 343 

metallization of, 339, 340 
Foot-lathes, 116, 117 
Force, coercive, 10 

or power, 27 
Forks and spoons, slinging wires for, 
222 
extra heavy coating of silver on 
the convex surfaces of, 230, 
231 
Frosting or satin finish, brushes for, 

105 
Fundamental system, 27 



GALVANI, L., discovery of con- 
tact-electricity by, 1 
Galvanic elements, 29-46 
Galvanometer, astatic, 20 

deductions drawn from the posi- 
tion of the needle of the, 85-87 
horizontal, 80 
indications by the, 83-87 
sine, 20 

tangent, 20 * 

vertical, 80 
Galvanometers, 20 

Galvanoplastic art, progress in the, 5 
baths, contrivances for the motion 
of, 312, 313 
current densities for, 311 
determination of free acid 
in, 313, 314 
of the content of copper 
in, 314, 315 
copy, to make a, directly from a 

metallic surface, 329, 330 
deposition in the cell- apparatus, 

303-308 
depositions by the battery and 
dynamo-machine, 308-313 
current-strength for, 324 
dynamo for, 309 
with a separate source of 
current, copper baths for, 
310 
method for originals in high re- 
lief, 340, 341 
operations in gold and silver, 
346, 347 
in iron, 344, 345 
in nickel, 345, 346 
process, discovery of the, 4, 5 
reproduction of busts, vases, etc, 
333-338 
Galvanoscopes, 20 



418 



INDEX. 



Galvanoplasty, 301-347 

classes of processes in, 302, 303 
definition of, 301 
investigators and practitioners of T 
8 
Gas carbon, anodes of, 154 
Gauduin's copper bath, 197 
Gauze and wire, metallic, gilding of, 

260-262 
Gelatine moulds, 341, 342 
Gerhold's baths for tinning by eon- 
tact, 286 
German silver, deposition of, 187, 
188 
for spoons, preparation 
of, for plating, 229, 
230 
gilded, stripping of, 273 
pickling of, 127 
preparation of, for sil- 
vering, 222 
removing oxide from, 

133 
sheets, grinding of, 1 1& 
silvering of, 229 
Gilded articles, matt for, 265, 266 

removing gold from, 272, 
273 
Gilder's wax, 259, 260 
Gilding by contact, by immersion, 
and by friction, 262-267 
by dipping, baths for, 266, 267 
by friction, 268, 269 
by weight, 256 
cold, bath for, 248, 249 

with yellow prussrate of 
potash for" 249 
coloring of the, 259, 260 
combination process of fire gild- 
ing with eleetro-deposition for,. 
271, 272 
eurrent-strengtb for, 254, 255 
dead, 257-259 

defective, treatment of, 265, 266 
execution of, 253-256 
fire or mercury, 269-271 
genuine, determination of, 273 
green, 257 
greenish, 259 
hollow ware, 255 
hot, bath for, 249, 250 
improving bad tones of, 260 
in the cold bath, 255, 256 
in the hot bath, 256 
metallic wire and gauze, 260- 
262 



Gilding — 

old dead, improving of, 272 
platinum anodes for, 251, 252 
porcelain and glass, 267, 268 
quicking articles before, 254 
red, 256, 257 
reddish, 259 
rose-color, 257 
without a battery, 253, 254 
with the cork, 268, 269 
with the rag, 268, 269 
with the thumb, 268, 269 
Glass balloons and flasks, 387 
gilding of, 267, 268 
jars, 387 

metallization of, 344 
platinizing of, 280 
Glauber's salt, 379 
Gold amalgam, preparation of, 269 
baths, 24 7-251 

heating of, 252, 253 
management of, 251-253 
preparation of, with the as- 
sistance of the current, 
251 
recovery of gold from, 274, 

275 
vats for, 252 
burnt, 264 
chloride, 374 

solution, preparation of, 
263-265 
deposition of, 246-275 
deposits, polishing of, 124, 251 
fineness of, 247 
fulminating, 374 
galvanoplastic operations in, 346, 

34 7 
incrustations with, 240, 241, 260 
native, composition of, 246 
properties of, 246, 247 
recovery of, from gold baths, 

274, 275 
removal of, from gilded articles, 

272, 273 
solder, 401 

solutions, agate vessels for, 89 
varnishers, mode of operation of, 
360, 361 
Goldworkers, bichromate element for, 

44, 45 
Gore, brass bath recommended by, 
208 
discovery of the explosive power 

of antimony chloride by, 297 
experiments of, 140, 141 



INDEX. 



419 



Gore — 

stopping-off varnish recommended 
.by, 231 
Gountier's solution for bronzing iron, 

211 
Goze's aluminium bath, 300 
Grained surface, production of a, by 

pickling. 131 
Graining,' 237-240 

preparations for, 238, 239 
Gramme armature, 54, 56 

dynamo-machines, 8, 56, 57 
Grasses, coating of, with copper, 343 
Gray, discovery of, 11 
Grease, removal of, 131, 132 
Green vitriol, 380, 381 
Grinding, 112-116 

disks, treatment of, 113 
wooden, 112 

lathes, 113-115 

transmission for, 75, 76 

rooms, 75, 76 
Grove, element of, 33, 34 
Giilcher's thermo-electric pile, 49, 50 
Gun-barrels, coating of, with super- 
oxide of lead, 292 
Gun-metal, composition of, 203 
Gutta-percha, introduction of, 5 

moulding in, 315-317 

moulding round articles in, 334, 
335 



HANSON &VAN WINKLE CO., 
belt strapping attachment 
manufactured by the, 119, 
120 
bicycle-power plating dyna- 
mo of the, 68 
lathe manufactured by the, 

117-119 
new dynamo electro-plating 

machine of the, 65-68 
rheostats patented and man- 
ufactured by the, 81-84 
Hard solder, 400 
Hartshorn, spirits of, 369 
Hassauer's copper bath, 193 
Hauck's thermo-electric pile, 48, 49 
Heads, section of, for moulding, 334 
Heat units produced by one cubic 

meter of coal gas, 50 
Hefner- A lteneck, dynamo- machine 

of, 8 
Heliography, 332, 333 
Helix, definition of a, 11 



Hess's solution for transferring any 
copper-zinc alloy serving as anode, 
208, 209 
Hooks and eyes, silvering of, 236, 237 
Hooks, tinning of, 287 
Horn silver, 373, 374 
Horse-power, English, 28 

French, 28 
Hubl, Von, current-densities for gal- 
vanoplastic baths according to, 
311 
experiments on copper by, 302 
Hydraulic press, 316 
Hydrochlorate of zinc, 372, 373 
Hydrochloric acid, 366 
Hydrocyanate of silver, 377 

of zinc, 376, 377 
Hydrocyanic acid, 366, 36 7 
poisoning by, 363 
Hydrometer, determination of the 

density of the baths by the, 136 
Hydrometers, 388, 389" 

table showing readings of dif- 
ferent, 389 
Hydroplatinic chloride, 374 
Hydrosulphate of ammonia, 370 
Hydrosulphuric acid, 369, 370 
Hygienic rules for the workshop, 361 

-364 
Hyponitric gas, poisoning by, 364 



TDIO-ELECTRICS, 11 

X Incrustations with silver, gold, 

and other metals, 240, 241 
Induced current, 22 
Induction, 21-23 

definition of, 21, 22 
Inductive current, 22 
Instruments and apparatus, various, 

387-392 
Internal resistance, 16 
International Congress of 1881, units 

adopted by the, 27, 28 
Ions, 24 

Iridescent colors, 293 
Iron-ammonium sulphate, 381 

articles, bath for tinning, 282, 
283 
copper baths for, 193-195 
coppering or brassing of, be- 
fore nickelling, 157 
grinding of, 115, 116 
silvered, stripping of, 243 
baths, management of, 296 
blue on, 356 



420 



INDEX. 



Iron — 

brassing of, 205, 206, 208 
bronze Barbedienne on objects 

of, 353 
bronzing solution for, 211 
brown-black coating with bronze 

lustre on, 356, 357 
castings, unground, brassing of, 

210 
coating articles of, with super- 
oxide of lead, 292 
coloring of, 356, 357 
deep black deposit of, 295, 296 
density of current for nickelling, 

159 
deposition of, 293-296 
galvanoplastic operations in, 344, 

345 
gilded, stripping of, 272 
lustrous black on, 356 
nickel bath for, 151 
objects, pickling of, 126 

removing oxide from, 133 
ore, magnetic, 9 
pickle for, 126 
protosulphate, 380, 381 
sheet, nickelling of, 177, 178 
silvering of, 231 
silvery appearance with high 

lustre on, 357 
sulphate, 380, 381 
tinning solution for, 286, 287 
vat, enamelled, 89 
wire and plates, table of the 

weight of, 406 
zinc bath for, 289, 290 
zincking of, by contact, 291 



TACOBY, Prof., discovery of the 
pj galvanoplastic process by, 4 
Jars, glass, 387 

Jordan, C. J., claim to the discovery 
of the galvanoplastic process bv, 
4, 5 
Joule, law of, 27 



KAISER'S process of depositing an 
alloy containing nickel, 186, 187 
Reiser & Schmidt's bichromate bat- 
tery, 43 
Rettles, 138, 139 
Klein's steel bath, 294 
Rnaffe and Riefer, description of a 
new element by, 41, 42 



Rnife-blades, nickelling of, 181, 182 
Knight, S. P., black-leading process 

of, 319, 320 
Rristaline, 358, 359 
Rroettlinger dynamo-machine, 61, 62 



LACES, coating of, with copper, 342 
Lacquering, 357-361 
Lacquers and varnishes, cellulose, 

358, 359 
Lahmeyer dynamo-machine, 62-64 
Lallande and Chaperon element, 39, 

40 
Lamp feet, cast zinc, nickelling of, 160 
Lang, L., & Son, patent of, for 

nickelling wire gau2e, 180, 181 
Lathe goblet scratch- brush, plater's, 
105 
scratch-brush, 122, 123 
Lathes, grinding, 113-115 

transmission for, 75, 76 
polishing, 116-120 
Law, Coulomb's, 11, 13 

general, of the action of two 
electrified wires on each other, 
21 
Joule's, 27 
Ohm's, 3, 4, 15, 16 
Laws, electrolytic, Faraday's, 25, 26 
Lead acetate, 386 
baths, 292 

deposition of, 292, 293 
properties of, 292 
removing oxide from, 133 
salts, poisoning by, 363 
superoxide of, coating gun-bar- 
rels and other articles of steel 
or iron with, 292 
Leading by contact, 292 
Leather, plates for the production of 

imitations of,. 343 
Leaves, coating of, with copper, 343 

metallization of, 339, 340 
Leclanche element, 39 
Length, unit of, 27 
Lenoir's process, galvanoplastic meth- 
od for originals in high relief, 340, 
341 
Lime, burnt or quick, 369 

mixture, preparation of, 132 
Vienna, 113, 120 
Line, neutral, 9 

Lines of force, region of the, 51 
Linseed oil, boiling, immersion of 
nickelled objects in, 124 



INDEX. 



421 



Litmus paper, test with, 147 
Liver of sulphur, 370 
Loadstone, 9 
Local action, 26 
Lunar caustic, 384 

Lye, hot, removing oily or greasy 
matter with, 132 



MAGNETIC field, 11, 51 
iron ore, 9 
machine, Woolrych's, 6 
meridian, 10 

needle, deflection of the, 3, 19 
determination of the position 
of the, to the conducting 
wire, 19 
poles, 9 
saturation, 1 
Magnetism, 9-11 

Ampere's tli eory of, 10 
and electricity, 9-28 
Magneto- and dynamo-electric ma- 
chines, 51-71 
Magneto-electric machine, definition 
of a, 52 
Siemens's, 7 
Siemens and Halske, 60, 

61 
transition of the, to the dy- 
namo-machine, 53, 54 
Wheatstone's, 7 
Magneto-machines, 54 
Magnets, artificial, 9 

field, 52 
Mainshaft, to find diameter of pulley 

on the, 407 
Marble, 378, 379 

Martin and Peyraud's process of gild- 
ing by friction, 268, 269 
Mass, unit of, 27 
Matrices, preparation of, in plastic 

material, 315-319 
Meidinger element, 33 
Melting-points of metals, table of, 401 
Mercuric nitrate, 384 
Mercurous nitrate, 383, 384 
Mercury or fire gilding, 269-271 

salts, poisoning by, 364 
Meriden Britannia Co. Works, prac- 
tice of silvering in the, 
228, 229 
silver plating solution 

used by the, 230 
striking solution used in 
the, 230 



| Meridian, magnetic, 10 
Meritens' process of coloring iron 

lustrous black, 356 
Metal, backing, 327 

reduction of a, from the solution 

of its salts, 1 
regaining of, from exhausted dip- 
ping baths, 130, 131 
white, silvering of, 228, 229 
Metallic articles, chemical treatment 
of, 126-134 
mechanical treatment of, 
before electro-plating, 
104-121 
mechanical treatment of, 
during and after the 
electro- plating process, 
121-126 
removal of oxide from, 133 
treatment of, 104-134 
powders, metallization by, 340 
Metallization by metallic powders, 340 

by the wet way, 338-340 
Metals, coloring, patinizing, oxidiz- 
ing, etc., of, 347-361 
conductivity of, 15 
creation of an electric current by 

the contact of various, 1 3 
deposition of several, from a com- 
mon solution, 210 
early deposition of, 6 
electro-deposited, porosity of, 121 
electro-deposition of, noticed by 

Cruikshank, 3 
grinding of, 115, 116 
incrustations with, 240, 241 
reduction of, without a battery, 

141-143 
table of the melting-points of 
some, 401 
Moire metallique, 282 
Molecules, Clausius's theory of, 24, 25 
Monopotassic carbonate, 378 
Montgomery, Dr., introduction of 

gutta-percha by, 5 
Mould, detaching the deposit from the, 
326 
wiring the, 321, 322 
Moulding in gutta-percha, 315-317 
in plaster of Paris, 335-337 
in wax, 317-319 
» with metallic allovs, 335 
Moulds, black-leading" the, 319-321 
gelatine, 341, 342 
metallization of, by the wet way, 
■ 338-340 



422 



INDEX. 



Moulds- 
plaster of Paris, to render imper- 
vious to fluids, 337, 338 
preparation of, in plastic mate- 
rial, 315-319 
Multipliers, 20 
Muriate of gold, 374 

of zinc, 372, 3 73 
Muriatic acid, 366 

Murray, discovery of black-leading 
by, 5 



MATURE printing, 342 

ll Needles, coppering of, 202 

tinning of, 288 
Negative electricity, 12 

wire, 87 
Neutral line or neutral zone, 9 
Newton and Weil's bronze bath, 211 
Nicholson and Carlisle, decomposition 

of water by, 2 
Nickel alloys, deposits of, 187, 188 
-ammonium sulphate, 382 
and cobalt, deposition of, 143- 

191 
anodes, 153-156 

reddish tinge of, 156 
articles, silvering of, 229 
bath, English formula for a, 152 
for small articles, 152 
illustration of coupling ele- 
ments for a, 76 
without nickel salt, 153 
baths, 144-152 

containing boric acid, 149- 

151 
for certain purposes, 151, 152 
freshly prepared, working of, 

152, 153 
preparation of, 144-147 
refreshing of, 167 
Boettger's observations on the 

deposition of, 5, 6 
carbonate, 379 
chloride, 373 
deposition of an alloy containing, 

186, 187 
deposits, polishing of, 124, 168 

scratch-brushes for, 122 
galvanoplastic operations in, 345, 

346 
patent for the deposition of, 5 
-plating, reasons for its popula- 
rity,^ 43, 144 
properties of, 144 



Nickel- 
recovery of, from old baths, 184 
-silver for spoons, preparation of, 

for plating, 229, 230 
sulphate, 382 

various colors on, 350, 351 
Nickelled articles, stripping of, 163- 
165 
objects, freeing of, from moisture, 
124 
Nickelling, 143-188 

bath, acid reaction of the, 145, 
146 
additions to the, 145, 146 
by contact and boiling, 185, 186 
criteria for judging the correct 

progress of, 158 
current-strength for, 157, 158 
dead, 168 

defective, to improve, 184, 185 
electrotvpes, cliches, etc, 182- 

184 
en masse of small and cheap ob- 
jects, 162, 163 
knife blades, sharp surgical in- 
struments, etc., 181, 182 
preparation of articles for, 156 
principal phenomena which may 
occur in, and means of avoid- 
ing them, 165-167 
remedy against the yellowish 

tone of, 165 
salts, prepared, 145 
sheet iron and sheet steel, 177, 

178 
sheet zinc, 168-177 
solid, 159 
test of, 159 
thick deposits of, 159 
tin plate, 177 
wire, 178-180 
wire gauze, 180, 181 
zinc sheet, current for, 175, 176 
Niel, composition of, 241 
Niel or nielled silvering, 241, 242 
Niello, Oorvin's, 342, 343 
Nitrates, 383, 384 
Nitre, 383 

spirit of, 366 
Nitric acid, 366 

table of the specific gravity 
and content of, 403 
Nitrous gas, poisoning by, 364 
Nobili, production of iridescent colors 

by, 4, 293 
Noe's thermo-electric pile, 46, 47 



INDEX. 



423 



Xon-eleetrics, 11 
Non-essential resistance, 1 6 
Norris and Johnson's brass bath, 208 
North pole, 10, 51 



OBERNETTER'S method of steel- 
ing copper printing plates, 294, 
295 
Object and anode wires, coupling the, 
with the resistance- boards, volt- 
meter, shunt and baths, description 
and illustrations of, 98-101 
Object wire, 87 

Oersted, Prof., discoveries of, 3 
Ohm, law of, 3, 4, 15, 16 

deduction from the, 19 
useful applications of the, 16, 
17 
Ohm, the, 28 
Oil of vitriol, 365, 366 
Orpiment, 371 

Over-nickelling or burning, 148, 158 
Oxide, removal of, 93, 133 
Oxidized silver, 242, 243 
Oxidizing, patinizing, coloring, etc., 
of metals, 347-361 



PACINOTTI, Dr. A., ring of, 7, 53 
Palladium baths, 281 
deposition of, 281 
properties of, 281 
Paracelsus, coating of metals by im- 
mersion known to, 1 
Paris mint, method of browning cop- 
per in the, 348 
Parkes' method of metallization, 339 
Patina, bronze-like, on tin, 357 
definition of, 347 
genuine, imitation of, 349, 350 
green, 351 
Patinizing, coloring, oxidizing, etc., 

of metal, 347-361 
Peyraud and Martin's process of gild- 
ing by friction, 268, 269 
Pianhauser, brass bath recommended 
by, 209 
copper bath according to, 197 
remedy against the yellowish tone 
of nickelling recommended by, 
165 
tin bath given by, 283, 284 
Philipp's process for coating laces and 

tissues with copper, 342 
Phosphates and pyrophosphates, 385 



Pickle for iron, 1 26 
for zinc, 127 
preliminary, 127 
Pickles, keeping of, 128 
Pickling, 126-131 
duration of, 126 
evolution of vapors in, and their 

absorption, 129, 130 
main points in, 129 
Pickling or dipping, 93 

production of a grained surface 
by, 131 
Pile of Volta, 2, 29 
Pilet's palladium bath, 281 
Pins, silvtring of, 236, 237 

tinning of, 287 
Pitchers, gilding the inner surface of, 

255 
Pixii, construction of the first electro- 
magnetic induction machine 
by, ,4 
electrical machine devised by, 53 
Planing or shaving-machine, types of, 

327, 328 
Plants, metallization of, 339, 340 
Plaster of Paris, moulding in, 335- 
337 
to make, impervious to 
fluids, 337, 338 
Plater's lathe goblet scratch-brush, 

105 
Plates, finishing the, 327, 328 

mounting of, 328 
Platinate bath, alkaline, 276, 277 
Platinic chloride, 374 
Plating balance, 225, 226 

section, 230, 231 
Platinizing by contact, 280 
execution of, 279, 280 
of glass, 280 
Platinum anodes, for gilding, 251, 
252 
baths, 275-279 

management of, 278, 279 
black, 275 

deposition of, 275-280 
deposits, polishing of, 124 
oxalate bath, 277", 278 
phosphate bath, 278 
properties of, 275 
recovery of, from platinum solu- 
tions, 280 
solutions, recovery of platinum 
from, 280 
Platoso-ammonium chloride, prepara- 
tion of, 276 



424 



INDEX. 



Plunge batteries, 42-44 

battery, Bunsen, 42, 43 
Poisoning by chemicals and the anti- 
dotes, 363, 364 
Polarization, 31 

Polarizing current, 25, 161, 162 
Pole, north, 10, 51 
pieces, 52 
south, 10, 51 
Poles, magnetic, 9 
Polishing, 116-121 
disks or bobs, 116 
in the tumbling drum, 110, 111 
lathes, 116-120 
machines, self-acting, 170-173 
materials, 1 20 
rooms, 75, 76 

formation of dust in the, 75 
zinc sheets, 1 70 
Poole, M., first use of thermo-elec- 
tricity by, 6 
Porcelain, gilding of, 267, 268 

metallization of, 344 
Positive electricity, 12 

wire, 87 
Potash, 3 77, 378 
-alum, 380 
bicarbonate of, 378 
caustic, 368, 369 
element, Duns's, 40, 41 
white prussiate of, 375, 376 
yellow prussiate of, 37 7 
Potassium and sodium, amalgams of, 4 
bitartrate, 385 
carbonate, 377, 378 

table of the specific gravity 
and content of solutions 
of, 401 
cyanide, 375, 376 

addition of, to silver baths, 

216, 217 
determination of the propor- 
tion to, in silver baths, 219 
introduction of the use of 
solutions of metallic cy- 
anides in, 5 
poisoning by, 363 
table to facilitate the use of, 
with different contents, 
376 
use of, as a pickle, 127, 128 
discovery of, 3 
ferro-cyanide, 37 7 
hydrate, 368, 369 
nitrate, 383 
sodium tartrate, 385, 386 



Potassium — 

stannate, preparation of, 287, 288 
sulphide, 370 
Potential, electrical, 14 

or electro-motive force, 28 
Powell, benzoic acid as an addition to 
nickel baths recommended by, 146 
Power or force, 27 
Press, hydraulic, 316 

toggle, 316 
Pretsch, invention of the heliographic 

process by, 332 
Primary current, 22 
Prime & Son, early deposition of 
metals by means of a permanent 
current of electricity by, 6 
Prussiate of silver, 377 

of zinc, 376, 377 
Prussic acid, 366, 367 

poisoning by, 363 
Pulley on countershaft carrying belt 
to machine, to find diameter 
of, 407 
on the mainshaft, to find diameter 
of, 407 
Pyrophosphates and phosphates, 385 



QUANTITY, 28 



RATSBANE, 367, 368 
R'auber, F., self-acting polishing 
machine of, 1 70-1 73 
Reaumur's thermometer, comparison 

of the scale of, 408 
Red sulphide of antimony, 371 
Reinbold's aluminium bath, 300 
Reproduction, 301-347 
Resinous electricity, 12 
Resist, composition of, 239, 240 
Resistance, 15, 28 
board, 79 

conditions upon which its 

action is based, 79, 80 
of the dynamo-machine, lo- 
cation of the, 95 
boards, voltmeter, shunt, and 
baths, coupling the, with the 
object- and anode-wires, de- 
scription and illustrations of, 
98-101 
essential or internal, 16 
non-essential or external, 16 
specific, 396 



INDEX. 



425 



Rheostat, 79 

Rheostats, patented and manufactured 
by the Hanson & Van Winkle Co., 
of Newark, N. J., 81-84 
Ring, Pacinotti's, 7, 53 
Rinsing apparatus, 92, 93 
Rochelle salt, 385, 386 
Rock salt, 3 71 
Rods, contrivance for protecting the, 

92 

Rogers, Wm., Manufacturing Co., 

amount of silver deposited 

upon tableware by the, 

223 

preparation of work for 

plating in the, 229, 230 
silver-plating solution used 

by the, 230 
striking solution used in the, 
230 
Roseleur, bath for silvering by im- 
mersion recommended by, 232- 
234 
baths for gilding recommended 
by, 249, 250 
for tinning by contact and 
immersion by, 286 
brass bath according to, 204, 205, 

208 
copper baths given by, 193, 195 
plating balance improved by, 

225, 226 
tin bath used by, 282 
Rouge, 120 

Ruolz, de, bronze bath according to, 
211 
deposition of metallic alloys bv, 

6 
progress in the galvanoplastic art 
due to, 5 



SAL AMMONIAC. 371 
solution, table showing the spe- 
cific gravity of, 403 
Salt, common, 371 
Saltpetre, 383 
Salts, conducting, 145 

nickelling, prepared, 145 
of the organic acids, 385-387 
Salzede's bronze bath, 211, 283 
Sand-blast, 108, 109 
Satin finish or frosting, brushes for, 

105 
Sawdust, 124 

box, 124 



Saw table, 327 

Saxton and Clarke, electric gener- 
ators constructed by, 53 
Scamoni, improvement of the helio- 

graphic process by, 332 
Scheele, observations of, 5 
Schuckert, S., dynamo-machine of, 

8, 57, 58 
Scratch-brush, hand, operating with 
the, 122 
lathe, 122, 123 
Scratch-brushes, various forms of, 104, 

105 
Scratch-brushing, 104, 107, 121-123 

decoctions used in, 122 
Secondary current, 22 
Section plating, 230, 231 
Seebeck, Prof,, discovery of a new 

source of electricity by, 46 
Seignette salt, 385, 386 
Shaving or planing machines, types 

of, 327, 328 
Sheet iron, nickelling of, 17 7, 178 

steel, nickelling of, 177, 178 
Shell, backing the, 326, 327 
Shultz's patent for removing hydro- 
chloric acid from the pores of cop- 
pered articles, 199 
Shunt, 98 

voltmeter, resistance-boards and 
baths, coupling the, with the 
object- and anode-wires, de- 
scription and illustrations of, 
98-101 
Siemens and Halske dynamo-ma- 
chine, 8, 61 " 
magneto-electric machine, 
60. 61 
Siemens, Dr. VV., discovery by, 53, 
54 
new form of armature devised 

by, 53 
magneto-electric machine of, 7 
Silver anodes, 215-221 

articles, gilding of, 254 
bath, illustration of coupling ele- 
ments for a, 76, 77 
baths, 213-215 

addition of potassium cyan- 
ide to, 216, 217 
agitation of the objects in 

the, 219, 220 
augmentation of, 217, 218, 

219 
current strength for, 215, 
216 



426 



INDEX. 



Silver baths — 

gradual thickening of, 218 
recovery of silver from old, 

245, 246 
treatment of, 215-221 
burnishing of, 227, 228 
calculating the weight of the de- 
posit of, from the density of 
current, 226 
chloride, 373, 3 74 

preparation of a bath with, 
213, 214 
coloring of, 357 

control of the weight of the de- 
posit of, 223, 224 
cyanide, 377 

preparation of a bath with, 
214 
dead white, coating of, 226, 227 
deposition of, 212-246 
deposits, polishing of, 124 

scratch-brushes for, 122 
determination of the actual con- 
tent of, in a silver bath, 219 
extra heavy coating of, on the 
convex surfaces of spoons and 
forks, 230, 231 
galvanoplastic operations in, 346, 

3-47 
heavy electro-deposit of, bath 

for, 213, 214 
incrustations with, 240, 241 
nitrate, 384 
oxidized, 242, 243 
plating solution used by the 
Meriden Britannia 
Co., 230 
used by the Wm. Rogers 
Manufacturing Co , 
230 
powder, mode of making, 238, 

239 
properties of, 212, 213 
recovery of, from old silver baths, 

245, 246 
solder, 400 
Silvered articles, imparting a yellow 
color to. 243 
stripping of, 243, 244 
Silvering by contact, by immersion, 
and cold silvering with paste, 
231-237 
by immersion, baths for, 232-237 
by weight, 221-228 

bath for, 213, 214 
cold, with paste, 237 



Silvering — 

electro-deposited, determination 

of, 214 
execution of, 221-231 
fine copper wire, 240 
iron, 231 

niel or nielled, 241, 242 
objections to the use of insoluble 

platinum anodes in, 216 
old (antique), 242 
ordinary, 228-231 
practice of, in the Meriden 

Britannia Works. 228, 229 
preparation of articles for, 221, 

222 
singular phenomenon in, 220, 221 
vats for, 215 
yellow tone of, 221 
Silverware, gilded, stripping of. 272, 

273 
Similor, composition of, 203 
Sine galvanometer, 20 
Siphons, 391 
Skates, removal of oily or greasy 

matter from, 132 
Slinging wires, 92 
Smee, A., discoveries of, 5 
element of, 31, 32 
experiments on copper by, 302 
introduction of the term " elec- 
tro-metallurgy" by, 5 
Soda, caustic, 369 

Sodium and potassium, amalgams 
of, 4 
bicarbonate, 378 
bisulphite, 382, 383 
carbonate, 378 
chloride, 371 
citrate, 387 
discovery of, 3 
hydrate, 369 
nitrate, 383 
phosphate, 385 
pyrophosphate, 385 
sulphide, preparation of solution 

of, 233, 234 
sulphite, 379, 382, 383 
Soft solder, 400 
Soldering fluid, 326 
Solders and alloys, table showing the 
composition of the most usual, 
398-401 
table of, 400, 401 
Solenoid, the, 10, 11, 21 
Solubility, table showing the, of 
various substances, 398 



INDEX. 



427 



South pole, 10, 51 

Spaeth, J. W., machine for gilding 
metallic wire and gauze by, 261, 
262 
Speed, rules for, 407 

to find the, of a machine, 407 
Spencer, T., claim to the discovery of 

the galvanoplastic process by, 4 
Spirit of nitre, 366 
Spirits of hartshorn, 369 
Spoons and forks, slinging wires for, 
222 
extra heavy coating of silver on 
the convex surfaces of, 230, 231 
Sprague, recommendation by, 162 
Stannic chloride, 372 
Stannous chloride, 372 
Stearine, moulding in, 317-319 
Steel articles, bath for tinning, 282, 
283 
copper baths for, 193-195 
coppering or brassing of, be- 
fore nickelling, 157 
grinding of, 115, 116 
silvering of, 229 
tinning solution for, 286, 287 
zinc bath for, 289, 290 
baths, 293, 294 
brassing of, 208 

coating articles of, with super- 
oxide of lead, 292 
density of current for nickelling, 

159" 
gilded, stripping of, 272 
objects, removing oxide from, 133 
pens, coppering of, 202 
sheet, nickelling of, 177, 178 
Steeling, 293-296 
by~contact, 296 
execution of, 296 
Stibium sulfuratum aurantiacum, 371 

nigrum, 370 
Stirring rods, 391, 392 
Stoehrer's battery, 45 
Stolba's method of tinning, 288 

process of nickelling by contact, 
185, 186 
Stopping-off", 231 

varnish, 231 
Striking solution, 228, 229, 2'!0 
Stripping cobalted copper plates, ex- 
periments in, 189, 190 
gilded articles. 272, 273 
nickelled articles, 163-165 
silvered articles, 243, 244 
Sugar of lead, 386 



Sulphates and sulphites, 379-383 
Sulphites and sulphates, 379-383 
Sulphur combinations, 369-371 

liver of, 370 
Sulphuretted hydrogen, 369, 370 
poisoning by, 364 
Sulphuric acid, 365, 366 

solutions, table show- 
ing the specific electri- 
cal resistances of dif- 
ferent, 396 
table showing the spe- 
cific gravity of, at 59° 
F., 402 
Sulphurous acid, poisoning by, 364 
Sulphydrate of ammonia, 370 
Sulphydric acid, 369, 370 
Surgical instruments, protection of 
wooden handles of, 344 
sharp, nickelling of, 181, 
182 
Switch-board, 79 



T 



ABLE for freeing articles from 
grease, 102, 103 
of chemical and electro-chemical 

equivalents, 394, 395 
of elements with their symbols, 
atomic weights, and specific 
gravities, 393 
of high temperatures, 401 
of the electro-motive force of 

elements, 397 
of the melting-points of some 

metals, 401 
of the resistance, and conductivity 

of pure copper, 404 
of the specific gravity and content 

of nitric acid, 403 
of the specific gravity and content 
of solutions of potassium car- 
bonate, 401 
of the weight of iron, copper, and 

brass wire and plates, 406 
showing actual diameters in deci- 
mal parts of an inch, corre- 
sponding to. the numbers 
of various wire gauges, 405 
the composition of the most 
usual alloys and solders, 
398-401 
the electrical resistance of 

pure copper wire, 404 
the solubility of various sub- 
stances, 398 



428 



INDEX. 



Table showing — 

the specific electrical resist- 
ances of different copper 
sulphate solutions, 396 
the specific electrical resist- 
ances of different sulphu- 
ric acid solutions, 396 
the specific gravity of sal 

ammoniac solutions, 403 
the specific gravity of sul- 
phuric acid at 59° F., 402 
the value of equal current 
volumes as expressed in 
amperes, 395, 396 
useful, 393-408 
Tangent galvanometer, 20 
Tanks or vats, 88-90 
Tartar emetic, 386 

Taucher, C, bath for gilding by con- 
tact recommended by, 263-266 
baths for hot gilding recom- 
mended by, 250, 251 
tin bath given by, 284, 285 
Temperatures, high, table of, 401 
Terchloride of gold, 374 
Terra cotta, metallization of, 344 
Thermo-electric couple, 46 
Thermo-electric pile, Clamond's, 47, 
48 
Gulcher's, 49, 50 
Hauck's, 48, 49 
Noe's, 46, 47 
Thermo-electric piles, 46-50 

advantages and disadvan- 
tages of, 50 
Thermo-electricity, 46 
first use of, 6 
Thermometers, comparison of the 
scales of the Fahrenheit, Cen- 
tigrade, and Reaumur, 408 
protection of the mercurv vessels 
of, 344 
Thompson, S. P., definition of a dy- 
namo-electric machine by, 52 
Time, unit of, 27 
Tin bath, alkalinp, 283 

bronze-like patina on, 357 
chloride, ,,372 
coloring of, 357 
dark coloration on, 357 
deposition of, 282-288 
deposits, polishing of, 124 
durable coating of, 287, 288 
plate, nickelling of, 177 
properties of, 282 
salt, 372 



Tin— 

sepia-brown on, 357 
Tin baths, 282-285 

management of, 285 
Tinning by contact and boiling, 286 

execution of, 285, 286 
Tissues, coating of, with copper, 342 
Toggle press, 3 1 6 
Tombac, composition of, 203 

deposits of, 212 

pickling of, 127 

removing oxide from, 133 
Touchstone, testing gold by the, 247 
Trough battery, 2, 29 
Tub or vat for cleansing objects, 92 
Tula niel, composition of, 241 
Tumbling drum or box, 109-111 
Twaddell's hydrometers, 388 



UNIT of length, 27 
of mass, 27 
of time, 27 
Units, electric, 27, 28 

practical, 28 
Urquhart, plan for recovering nickel 
from old solutions proposed bv, 
184 



VAPORS, acid, plant for absorbing, 
129, 130 
Varnish, stopping-off, 231 
Varnishes and lacquers, cellulose, 358, 
359 
different shades of, used by gold 
varnishers, 360, 361 
Varrentrapp's steel bath, 293, 294 
Vases, galvanoplastic reproduction of, 

333, 338 
Vat or tub for cleansing objects, 92 
Vats for gold baths, 252 
for silvering, 215 
or tanks, 88-90 
Verdigris, 386 
Vienna lime, 113, 120 
Vitreous electricity, 12 
Vitriol, blue, 381 

table of the content of, 307 
green, 380, 381 
oil of, 365, 366 
white, 381 
Volt, the, 28 

Volta, A., discoveries by, 1, 2 
Volta, pile of, 2, 29 
Voltaic pile, 2, 29 



INDEX. 



429 



Voltameter, 25 

Voltmeter, 95, 96 

resistance - boards, shunt and 
baths, coupling the, with the 
object- and anode-wires, de- 
scription and illustrations of, 
98-101 



WAHL, Dr. W. H., directions for 
preparing platinum baths by, 
276-278 
Walenn's copper bath, 197 
Warren, cobalt solution recommended 

by, 190 
Washing soda, 378 
Watch movements, plating of, with 

palladium, 281 
Watch-works, brush used by the 

gilder of, 107 
Watches, gilding grained parts of, 
240 
graining parts of, 237-240 
Water, decomposition of, 2, 23 

importance of the constitution of, 

134, 135 
rinsing and cleansing, facilities 
for the renewal of the, 74 
Watt's process of depositing German 

silver, 188 
Watt, the, 28 

Wax, moulding in, 317-319 
Weil, copper bath by, 196, 197 

and Newton's bronze bath, 211 
Weiler, L., conductivity of metals 

according to, 15 
Weston, boric acid as an addition to 
nickel baths, recommended by, 
146 
dynamo-machine, 8, 64, 65 
nickel baths recommended by, 
149 
Wheatstone, Sir C, discovery by, 53, 
54 
' magneto-electric machine of, 7 
Wliite arsenic, 367, 368 

metal, silvering of, 228, 229 
prussiate of potash, 375, 376 
vitriol, 381 
Whiting, 378, 379 
Wilde machine, 6 

Wire and gauze metallic, gilding of, 
260-262 
carriers, 95 
fine copper, silvering of, 240 



Wire — 

gauges, table showing actual dia- 
meters in decimal parts of 
an inch corresponding to 
the number of various, 
405 
gauze, nickelling of, 180, 181 
negative or object, 87 
nickelling of, 178-180 
positive or anode, 87 
Wires, calculating the thickness of, for 
dynamo-machines, 103 
conducting, 87, 88 
object and anode, insulation of, 

94, 95 
slinging, 92 

tying the objects to, 132, 133 
Wollaston, electro-coating of silver 

by, 2, 3 
Woolrych, magnetic machine con- 
structed by, 6 
Wood, coating of, with a galvano- 
plastic deposit of copper, 244 
floors, 74 
Work, 28 

Working-room, floor of the, 74 
heating of the, 73 
light and ventilation of the, 

72, 73 
size of the, 74 
Workshop, hygienic rules for the, 

361-364 
Wright, introduction, of the use of 
solutions of metallic cyanides in 
potassium cyanide by, 5 
Wrought iron, brassing of, 208 

bronzing solution for, 211 
objects, pickling of, 126 
zinc bath for, 289, 290 



T7ELLOAV prussiate of potash, 377 



ZACHERS, Tulanielof, 241 
Zapon, 358 
Zilken's bath for tinning by contact, 

286 
Zinc alloys, production of, by the 
galvanic method, 291, 292 
amalgamation of the, of elements, 

30, 31 
articles, copper baths for, 195 
baths, 289, 290 



430 



INDEX. 



Zinc — 

black on, 355 

blue-black on, 355 

brassed, bronze Barbed ienne on, 

353 
brassing of, 208 
bronzing on, 355 
carbonate, 3 79 
castings, treatment of, 116 
cast, nickelling lamp feet of, 160 
chloride, 372, 373 

and ammonium chloride, 3 73 
coloring of, 355, 356 
coppering of, 201 
cyanide, 376, 377 
dead gilding on, 25S, 259 
density of current for nickelling, 

159 
deposition of, 289-292 
deposits, scratch- brushes for, 122 
gray on, 355 
nickel bath for, 151 
nickelling salts for nickelling, 145 
objects, bath for tinning, 282 

pickling of, 127 
pickle for, 127 
plates, coppering of, 201 



Zinc — 

properties of, 289 
red-brown color on, 356 
sheet, anodes for nickelling, 1 76 
brassing of, 1 74, 1 75 
coppering of, 174, 175 
current for nickelling, 1 75, 

176 
freeing of, from grease, 1 73 
nickelled, black streaks and 

stains on, 1 76 
nickelling of, 168-177 
polishing of, 170 
treatment of, 116 
sulphate, 381 

yellow-brown shades on, 356 
Zincking, execution of, 290, 291 

iron by contact, 291 
Zone, neutral, 9 
Zozimus, simple reduction of metals 

known to, 1 
Zucker & JLevett Chemical Co., car- 
boy-stand manufactured 
by the, 134 
improved American giant 
dynamo of the, 68-70 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 



Electro-plating Outfits 



FOR 



GOLD, SILVER, NICKEL, COPPER, Etc. 

m 










a 



m 






WE FURNISH COMPLETE OUTFITS FOR 



... 



Electro-plating, Polishing, Buffing, Burnishing 
and Lacquering. 

SEND FOR ILLUSTRATED CATALOGUE SHOWING 



DYNAMOS, 
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FELT WHEELS, 
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ANODES, 
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CROCUS. 



THE HANSON & VAN WINKLE CO. 

MANUFACTORY AND OFFICES: 

219 & 221 MARKET STREET, NEWARK, N. J., U. S. A. 

New York Office: 81 Liberty Street. 
Western Branch: 35 and 37 S. Canal Street, Chicago. 

J. E. HARTLEY & CO., Sole European Agents, 
St. Paul's Square, Birmingham. 



The Largest Manufacturers of EIectro=plating and Polishing 
Material and Apparatus. 

(i) 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 



The New H. & V. W. Dynamo. 




We are now ready to send out eight sizes of our new and improved 
Dynamo, which we are safe in guaranteeing thirty per cent, more power- 
ful than an}' other machine sold at same price. 

The following are some of the many advantages offered : 

The Field Magnets have wrought iron in them, vastly superior to 
cast iron. 

The Magnets have a round core, which for a given amount of wire 
is much more powerful. 

They have a very short magnetic circuit — a very good point. 

The Commutator is easily taken off, so as to renew the segments, 
which are made of tempered copper, and are very durable. 

The Armature and working parts are away from the base, and are 
protected fully from dirt. 

The Field Magnets are wound on bobbins and are easily replaced, no 
return of machine and expensive repairs ever being required. 

Clean lubrication, requiring attention but once a week. No oil to 
get in Armature like all other Dynamos. 

Appearance : Without sacrificing the electrical efficiency of the 
machine, it is the most attractive in the market, and consequently will 
receive more care from those in charge. 



(2) 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 





Price List of the New Hanson & 


Van Winkle Dynamo. 




Capacity. 


Pulley. 


Connecting 
Wire. 


Weight. 


Price. 




Nickel. 


Silver 
Per Hour. 






No. I, 

No. 2, 
No. 3, 
No. 4, 
No. 5 , 
No. 6, 
No. 7, 
No 8 


2oo galls. 

700 " 
1 , 200 ' ' 
2,000 " 
3,000 " 
4,5°° " 


12 OZ. 

40 " 

75 " 
175 " 
300 " 

.45o " 


1,800 
1,500 
1,500 
1,300 
1,100 
900 


4x2 

5X2^ 

6x3 

7x4 

9X5 

9X5 


No. 4, 
No. 0, 
No. 000, 
No. 0000, 
y& inch, 
1 inch, 


125 lbs. 
250 " 
400 " 
610 " 
1,040 " 
1 , 200 ' ' 


$100.00 
225.00 
300.00 
400.00 
500.00 
600.00 
700.00 






800.00 








j t- t- 








These machines will be placed on 30 days' trial with responsible 
parties, and, if not satisfactory, may be returned at our expense. 




OUR No. 3 STANDARD BUFFING LATHE, 

with or without column, 

has the largest safe of any in the market. 

POLISHING AND BUFFING LATHES. All Sizes. 



FELT WHEELS, 
WALRUS WHEELS, 
WOOD WHEELS, 
CANVAS WHEELS, 
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PAPER WHEELS, 



MUSLIN BUFF WHEELS, 
COTTON FLANNEL WHEELS, 
BRISTLE WHEELS, 
TAMPICO WHEELS, 
BRASS SCRATCH WHEELS, 
STEEL SCRATCH WHEELS, 



We manufacture and carry in stock a complete line of Polishing and 
Buffing machinery, and every description of wheels for finishing metals, 
from the casting to final buffing. Send for illustrated catalogue. 



(3) 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 




No. 500 
FOOT=POWER LATHE AND POLISHING MATERIALS. 

No. 2 Lathe shown above $18.00 

Complete box of polishing tools and powders for small work . . . 3.00 

For description of above Lathe and appliances see Fig. 106, page 336. 

Polishing Outfits for all purposes. We are the largest manufacturers 
of fine steel and Brass Wire Scratch Brushes, Platers' Brushers, Bristle, 
Tampico, etc. 

(4) 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 



PROCESS OF ELECTROPLATING BY 

BICYCLE=POWER PLATING DYNAMO. 

When batteries are used and the work does not come out satisfactory, 
there are several places that the plater has to look for trouble. First 
with the condition of the solution ; then the plates, and then the acid- 
destroyed connections and contacts. With the use of the dynamo the 
operator at once has a reliable current. Ready at all times. Never out 
of condition. Costing nothing when in idleness except interest upon 
investment, and when in operation but a little exercise from the operator. 

The only reason that the dynamo has not come into use in this field 
has been the want of suitable hand or foot power. This pioneer work in 
the way of getting the most power out of man and at the same time at 
the least exertion, has been accomplished for us by the invention and 
rapid improvements in the bicycle. There is no disputing this fact. 
Many attempts have been made with hand powers for propulsion, but 
they now all concede that the foot power is the most efficient. We take 
advantage of these facts and adopt this method of power and still have 
the operator's hands at leisure to attend to other work, solutions, etc., 
while the plating is in progress. 

This 'machine is designed for Jewelers, Silversmiths, Training 
Schools, Bicycle Dealers and Repairers, and wherever a moderate 
current is desired for doing plating on a small scale. 



ifef^f 



Vfcfc 





SHOWING HACHINE READY FOR 
POLISHING. 



(5) 



THE HANSON & VAN WINKLE CO., NEWARK, N. J., U. S. A. 



SHOWING MANNER OF USING OUR PATENT LACQUERS. 




PATENT KRISTALINE— A Dip Lacquer 

For protecting the surface of metals of all kinds with an indestruc- 
tible, Glass-like Coating or Transparent Enamel, that will resist Acids, 
Alcohol, Oils, Water, etc., and so hard as not to scratch like ordinary 
lacquer. 

It is used on the most highly polished metals without affecting finish 
or color, as well as on the delicate shades of color produced by various 
metallic solutions, oxidizing, etc. 

KRISTALINE AND ZAPON. 

Copyrighted and Patented. 
DIRECTIONS FOR USING KRISTALINE AND ZAPON. 

i. Use a tin-lined, wooden tank for holding the lacquer. 

2. Have the work as clean as for plating. 

3. Hang the articles so that the lacquer will run off freely. 

4. Allow them to drip over the dripping tank until the lacquer stops 
flowing. 

5. Dry in a temperature of 150 degrees, if convenient. These 
lacquers will dry without heat, but baking improves the finish. 

6. Use the lacquers as shipped until they show a drip or nipple in 
drying. 

7. Thin only with Kristaline or Zapon Thinner. 

When ordering give full information as to the class of work to be 
lacquered, or order by following grade marks. 

KRISTALINE. ZAPON. 

For silver grade S. For silver grade K. 

For brass, bronze, etc. . . "X. For brass, bronze, etc. . . " L. 
For electro-plate and oxi- For electro-plate and oxi- 
dized work " W. dized work " M. 

FOR SPECIAL PURPOSES. 
KRISTALINE- ZAPON. 

For wooden articles . . - grade P. For oxidizing and 

For insulating " I. enameling, . . . grade Black. 

For brushing .... " AX. 
Gold Lacquers. All shades. 

THE HANSON & VAN WINKLE CO., 

NEWARK, N. J., U. S. A., 

Who ficrnish everything. 

(6) 



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BARR. — A Practical Treatise on the Combustion of Coal: 
Including descriptions of various mechanical devices for the Eco- 
nomic Generation of Heat by the Combustion of Fuel, whether solid, 
liquid or gaseous. 8vo. ....... $2.50 

BARR. — A Practical Treatise on High Pressure Steam Boilers: 
Including Results of Recent Experimental Tests of Boiler Materials, 
together with a Description of Approved Safety Apparatus, Steam 
Pumps, Injectors and Economizers in actual use. By Wm. M. Barr. 
204 Illustrations. 8vo. ....... $3.00 

BAUERMAN.-A Treatise on the Metallurgy of Iron : 

Containing Outlines of the History of Iron Manufacture, Methods of 
Assay, and Analysis of Iron Ores, Processes of Manufacture of Iron 
and Steel, etc., etc. By H. Bauerman, F. G. S., Associate of the 
Royal School of Mines. Fifth Edition, Revised and Enlarged. 
Illustrated with numerous Wood Engravings from Drawings by J. B. 
Jordan. i2mo. $2.oc 

BAYLES. — House Drainage and Water Service : 

In Cities, Villages and Rural Neighborhoods. With Incidental Con- 
sideration of Certain Causes Affecting the Healthfulness of Dwell- 
ings. By James C. Bayles, Editor of " The Iron Age " and " The 
Metal Worker." With numerous illustrations. 8vo. cloth, 

BEANS. — A Treatise on Railway Curves and Location of 
Railroads : 
By E. W. Beans, C. E. Illustrated. i2mo. Tucks . #1.50 

BECKETT.— A Rudimentary Treatise on Clocks, and Watches 

and Bells : 

By Sir Edmund Beckett, Bart, LL. D., Q. C. F. R. A. S. With 

numerous illustrations. Seventh Edition, Revised and Enlarged. 

l2mo $2.2$ 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BELL. — Carpentry Made Easy: 

Or, The Science and Art of Framing On a New and Improved 
System. With Specific Instructions for Building Balloon Frames, Barn 
Frames, Mill Frames, Warehouses, Church Spires, etc. Comprising 
also a System of Bridge Building, with Bills, Estimates of Cost, and 
valuable Tables. Illustrated by forty-four plates, comprising PieaiW 
200 figures. By William E. Bell, Architect and Practical Builder. 
8vo. #5-oa 

BEMROSE.— Fret-Cutting and Perforated Carving: 

With fifty-three practical illustrations. By W. Bemrose, Jr. I vol- 
quarto .......... $2.50 

BEMROSE.— Manual of Buhl-work and Marquetry: 

With Practical Instructions for Learners, and ninety colored designs. 
By W. Bemrose, Jr. I vol. quarto .... £3.00 

BEMROSE.— Manual of Wood Carving: 

With Practical Illustrations for Learners of the Art, and Original and 
Selected Designs. By William Bemrose, Jr. With an Intro- 
duction by Llewellyn Jewitt, F. S. A., etc. With 128 illustra- 
tions, 4to. ......... #2.53 

BILLINGS.— Tobacco : 

Its History, Variety, Culture, Manufacture, Commerce, and Various 
Modes of Use. By E. R. Billings. Illustrated by nearly 200 
engravings. 8vo. . . ; . . • . . $3-°G 

BIRD. — Tbe American Practical Dyers' Companion: 

Comprising a Description of the Principal Dye-Stuffs and Chemicals 
used in Dyeing, their Natures and Uses; Mordants, and How Made; 
with the best American, English, French and German processes for 
Bleaching and Dyeing Silk, Wool, Cotton, Linen, Flannel, Felt. 
Dress Goods, Mixed and Hosiery Yarns, Feathers, Grass, Felt, Fur, 
Wool, and Straw Hats, Jute Yarn, Vegetable Ivory, Mats, Skins, 
Furs, Leather, etc., etc. By Wood, Aniline, and other Processes, 
together with Remarks on Finishing Agents, and Instructions in the 
Finishing of Fabrics, Substitutes for Indigo, Water-Proofing of 
Materials, Tests and Purification of Water, Manufacture of Aniline 
and other New Dye Wares, Harmonizing Colors, etc., etc. ; embrac- 
ing in all over 800 Receipts for Colors and Shades, accompanied by 
170 Dyed Samples of Rarv Materials and Fabrics. By F. J. Bird, 
Practical Dyer, Author of " The Dyers' Hand-Book." 8vo. $10.00 

BLINN. — A Practical Workshop Companion for Tin, Sheet- 
Iron, and Copper-plate Workers : 
Containing Rules for describing various kinds of Patterns used by 
Tin, Sheet-Iron and Copper-plate Workers; Practical Geometry; 
Mensuration of Surfaces and Solids ; Tables of the Weights of 
Metals, Lead-pipe, etc. ; Tables of Areas and Circumference* 
of Circles; Japan, Varnishes, Lackers, Cements, Compositions, etc., 
etc. By Leroy J. Blinn, Master Mechanic. With One Hundred 
and Seventy Illustrations. l2mo. . . . . . #2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BOOTH. — Marble Worker's Manual: 

Containing Practical Information respecting Marbles in general, theil 
Cutting, Working and Polishing ; Veneering of Marble ; Mosaics ; 
Composition and Use of Artificial Marble, Stuccos, Cements, Receipts, 
Secrets, etc., etc. Translated from the French by M. L. Booth. 
With an Appendix concerning American Marbles. i2mo., cloth $1.50 
BDOTH and MORFIT. — The Encyclopaedia of Chemistry, 
Practical and Theoretical : 
Embracing its application to the Arts, Metallurgy, Mineralogy, 
Geology, Medicine and Pharmacy. By James C. Booth, Melter 
and Refiner in the United States Mint, Professor of Applied Chem- 
istry in the Franklin Institute, etc., assisted by Campbell Morfit, 
author of " Chemical Manipulations," etc. Seventh Edition. Com- 
plete in one volume, royal 8vo., 978 pages, with numerous wood-cuts 
and other illustrations . . . . . . - $3-5° 

BRAM WELL.— The Wool Carder's Vade-Mecum* 

A Complete Manual of the Art of Carding Textile Fabrics. By W. 
C. Bramwell. Third Edition, revised and enlarged. Illustrated. 
Pp. 400. i2mo #2.50 

BRANNT. — A Practical Treatise on Animal and Vegetable 
Fats and Oils : 
Comprising both Fixed and Volatile Oils, their Physical and Chemi- 
cal Properties ana Uses, the Manner of Extracting and Refining 
them, and Practical Rules for Testing them ; as well as the Manu- 
facture of Artificial Butter, Lubricants, including Mineral Lubricating 
Oils, etc., and on Ozokerite. Edited chiefly from the German of 
Drs. Karl Schaedler, G. W. Askinson, and Richard Brunner, 
with Additions and Lists of American Patents relating to the Extrac- 
tion, Rendering, Refining, Decomposing, and Bleaching of Fats and 
Oils. By William T. Brannt. Illustrated by 244 engravings. 
739 pages. 8vo #7.50 

BRANNT. — A Practical Treatise on the Manufacture of Soap 
and Candles : 
Based upon the most Recent Experiences in the Practice and Science ; 
comprising the Chemistry, Raw Materials, Machine ,- v. and Utensils 
and Various Processes of Manufacture, including a great variety of 
formulas. Edited chiefly from the German of Dr. C. Deite, A. 
Engelhardt, Dr. C. Schaedler and others; with additions and lists 
of American Patents relating to these subjects. By Wm. T. Brannt. 
Illustrated by 163 engravings. 677 pages. 8vo. . . $7.50 

BRANNT.— A Practical Treatise on the Raw Materials and the 
Distillation and Rectification of Alcohol, and the Prepara- 
tion of Alcoholic Liquors, Liqueurs, Cordials, Ritters, etc.: 
Edited chiefly from the German oi Dr. K. Stammer, Dr. F. Eisner, 
and E. Schubert. By Wm. T. Brannt. Illustrated by thirty-one 
engravings. 121110. ...... c $2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BRANNT— WAHL- The Techno-Chemical Receipt Book: 

Containing several thousand Receipts covering the latest, most ;m- 
portant, and most useful discoveries in Chemical Technology, an<j 
their Practic.il Application in the Arts and the Industries. Edited 
chiefly from the German of Drs. Winckler, Eisner, Heintze, Mier- 
ziriski, Jacobsen, Koller, and Heinzerling, with additions by Wm. 'J. 
Brannt and Wm. H. Wahl, Ph. D. Illustrated by 78 engravings. 
:;iuo, 495 pages . . ... #2 00 

HROWN. — Five Hundred and Seven Mechanical Movements; 
Embracing all those which are most important in Dynamics, Hy- 
draulics, Hydrostatics, Pneumatics, Steam-Engines, Mill and other 
Gearing, Presses, Horology and Miscellaneous Machinery; and in- 
cluding many movements never before published, and several of 
which have only recently come into use. By Henry T. Brown, 
i2mo. .......... gi.oo 

BUCKM ASTER.— The Elements of Mechanical Physics: 
By J. C. Buckmaster. Illustrated with numerous engravings. 
i2mo . $l.oo 

BULLOCK. — The American Cottage Builder : 

A Series of Designs, Plans and Specifications, from $200 to $20,000, 
for Homes for the People ; together with Warming, Ventilation, 
Drainage, Painting and Landscape Gardening. By John Bullock, 
Architect and Editor of "The Rudiments of Architecture and 
Building," etc., etc. Illustrated by 75 engravings. 8v'o. $3-5Q 

BULLOCK.— The Rudiments of Architecture and Building: 
For the use of Architects, Builders, Draughtsmen, Machinists, En- 
gineers and Mechanics. Edited by John Bullock, author of " The 
American Cottage Builder." Illustrated by 250 Engravings. 8vo. $3.50 

BURGH. — Practical Rules for the Proportions of Modern 
Engines and Boilers for Land and Marine Purposes. 
By N. P. Burgh, Engineer. i2mo. .... $1.50 

BYLES.— Sophisms of Free Trade and Popular Political 

Economy Examined, 

By a Barrister (Sir John Barnard Byles, Judge of Common 

Pleas). From the Ninth English Edition, as published by the 

Manchester Reciprocity Association. i2mo. . . . $1.25 

BOWMAN.— The Structure of the Wool Fibre In its Relation 
to the Use of Wool for Technical Purposes : 
Being the substance, with additions, of Five Lectures, deliverea dt 
the request of the Council, to the members of the Bradford Technical 
College, and the Society of Dyers and Colorists. By F. H. Bow- 
man, D. Sc, F. R. S. E.j F. L. S. Illustrated by 32 engravings. 
8vo $6.50 

tTYRNE. — Hand-Book for the Artisan, Mechanic, and Engi- 
neer: 
Comprising the, Grinding and Sharpening of Cutting Tools, Abva-.ve 
Processes, Lapidary Work, Gem and Glass Engraving, Varnishing 
and Lackering, Apparatus, Materials and Processes for Grinding and 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



Polishing, etc. By Oliver Byrne. Illustrated by 185 wood en- 
gravings. 8vo. ........ #5.00 

BYRNE. — Pocket-Book for Railroad and Civil Engineers: 
Containing New, Exact and Concise Methods for Laying out Railroad 
Curves, Switches, Frog Angles and Crossings; the Staking out of 
work; Levelling; the Calculation of Cuttings; Embankments; Earth- 
work, etc. By Oliver Byrne. i8mo., full bound, pocket-book 
form #1.75 

BYRNE. — The Practical Metal-Worker's Assistant : « 

Comprising Metallurgic Chemistry; the Arts of Working all Metals 
and Alloys; Forging of Iron and Steel; Hardening and Tempering; 
Melting and Mixing; Casting and Founding; Works in Sheet Metal; 
the Processes Dependent on the Ductility of the Metals; Soldering; 
and the most Improved Processes and Tools employed by Metal- 
workers. With the Application of the Art of Electro-Metallurgy to 
Manufacturing Processes; collected from Original Sources, and from 
the works of Holtzapffel, Bergeron, Leupold, Piumier, Napier, 
Scoffern, Clay, Fairbairn and others. By Oliver Byrne. A new, 

• revised and improved edition, to which is added an Appendix, con- 
taining The Manufacture of Russian Sheet-Iron. By John Percy, 
M. D., F. R. S. The Manufacture of Malleable Iron Castings, and 
Improvements in Bessemer Steel. By A. A. Fesquet, Chemist and 
Engineer. With over Six Hundred Engravings, Illustrating every 
Branch of the Subject. 8vo $5.00 

BYRNE.— The Practical Model Calculator: 

For the Engineer, Mechanic, Manufacturer of Engine Work, Naval 
Architect, Miner and Millwright. By Oliver Byrne. 8vo., nearly 
600 pages . . . . . ' . . . . $300 

CABINET MAKER'S ALBUM OF FURNITURE: 
Comprising a Collection of Designs for various Styles of Furniture. 
Illustrated by Forty-eight Large and Beautifully Engraved Plates. 
Oblong, 8vo ■ . . #2.00 

CALLINGHAM. — Sign Writing and Glass Embossing: 
A Complete Practical Illustrated Manual of the Art. By James 
Callingham. i2mo. ....... $1.50 

CAMPIN. — A Practical Treatise on Mechanical Engineering: 
Comprising Metallurgy, Moulding, Casting, Forging, Tools, Work- 
shop Machinery, Mechanical Manipulation, Manufacture of Steam- 
Engines, etc. With an Appendix on the Analysis of Iron and Iron 
Ores. By Fpancis Campin, C. E. To which are added, Observations 
on the Construction of Steam Boilers, and Remarks upon Furnaces 
used for Smoke Prevention ; with a Chapter on Explosions. By R. 
Armstrong, C. E., and John Bourne. Rules for Calculating the 
Change Wheels for Screws on a Turning Lathe, and for a Wheeta 
cutting Machine. By J. La Nicca. Management of Steel, Includ- 
ing Forging, Hardening, Tempering, Annealing, Shrinking and 
Expansion ; and the Case-hardening of Iron. By G. Ede. 8vg. 
Illustrated with twenty-nine plates and 100 wood engravings $5.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CAREY.— A Memoir of Henry C. Carey. 

By Dr. Wm. Elder. With a portrait. 8vo., cloth . . 75 

CAREY.— The Works of Henry C. Carey : 

Harmony of Interests : Agricultural, Manufacturing and Commer. 

cial. 8vo. . . $1.25 

Manual of Social Science. Condensed from Carey's " Principles 
of Social Science." By Kate McKean. i vol. i2mo. . #2.00 
Miscellaneous Works. With a Portrait. 2 vols. 8vo. #10.00 

Past, Present and Future. 8vo $2.50 

Principles of Social Science. 3 volumes, 8vo. . . $7.50 
The Slave-Trade, Domestic and Foreign; Why it Exists, and 
How it may be Extinguished (1853). 8vo. . . , #2.00 

The Unity of Law : As Exhibited in the Relations of Physical, 
Social, Mental and Moral Science (1872). 8vo. . . #2.50 

CLARK. — Tramways, their Construction and Working : 

Embracing a Comprehensive History of the System. With an ex- 
haustive analysis of the various modes of traction, including horse- 
power, steam, heated water and compressed air; a description of the 
varieties of Rolling stock, and ample details of cost and working ex-, 
penses. By D. KlNNEAR Clark. Illustrated by over 200 wood 
engravings, and thirteen folding plates. 2 vols. 8vo. . #12.50 

COLBURN.— The Locomotive Engine : 

Including a Description of its Structure, Rules for Estimating its 
Capabilities, and Practical Observations on its Construction and Man- 
agement. By Zerah Colburn. Illustrated. 121110. . $i.oa 

COLLENS.— The Eden of Labor; or, the Christian Utopia. 
By T. Wharton Collens, author of " Humanics," "The Historf 
of Charity," etc. l2mo. Paper cover, #1.00; Cloth . #1.25 

COOLEY. — A Complete Practical Treatise on Perfumery : 

Being a Hand-book of Perfumes, Cosmetics and other Toilet Articles. 
With a Comprehensive Collection of Formulae. By AR.NOLD J 
COOLEY. I21T10 #l.5& 

COOPER.— A Treatise on the use of Belting for t'he Trans- 
mission of Power. 
With numerous illustrations of approved and actual methods of ar- 
ranging Main Driving and Quarter Twist Belts, and of Belt Fasten, 
ings. Examples and Rules in great number for exhibiting and cal- 
culating the size and driving power of Belts. Plain, Particular and 
Practical Directions for the Treatment, Care and Manigement o 
Belts. Descriptions of many varieties of Beltings, together witn 
chapters on the Transmission of Power by Ropes; by Iron and 
Wood Frictional Gearing; on the Strength of Belting Leather; and 
on the Experimental Investigations of Morin, Briggs, and others. Bj 
John H. Cooper, M. E. 8vo #3-50 

CRAIK. — The Practical American Millwright and M^ler. 

By David Craik, Millwright. Illustrated by numerous wood en- 
gravings and two folding plates. 8vo. . . . * $3-50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CREW. — A Practical Treatise on Petroleum : 

Comprising its Origin, Geology, Geographical Distribution, History, 
Chemistry, Mining, Technology, Uses and Transportation. Together 
with a Description of Gas Wells, the Application of Gas as Fuel, etc. 
By Benjamin J. Crew. With an Appendix on the Product and 
Exhaustion of the Oil Regions, and the Geology of Natural Gas in 
Pennsylvania and New York. By Charles A. Ashburner, M. S . 
Geologist in Charge Pennsylvania Survey, Philadelphia Illustrated 
by 70 engravings. 8vo. 508 pages .... $^.00 

CROSS.— The Cotton Yarn Spinner: 

Showing how the Preparation should be arranged for Different 
Counts of Yarns by a System more uniform than has hitherto been 
practiced; by having a Standard Schedule from which we make all 
our Changes. By Richard Cross. 122 pp. 121110. . 75 

CRISTIANL— -A Technical Treatise on Soap and Candles: 
Willi a Glance at the Industry of Fats and Oils. By R. S. Cris 
TiANi, Chemist. Author of " Perfumery and Kindred Arts." Illus- 
trated by 176 engravings. 581 pages, 8vo. . . . $15.00 
CRISTIANL— Perfumery and Kindred Arts : 

A Comprehensive Treatise on Perfumery, containing a History of 
Perfumes from the remotest ages to the present time. A complete de- 
tailed description of the various Materials and Apparatus used in the 
Perfumer's Art, with thorough Practical Instruction and careful For- 
mulae, and advice for the fabrication of all known preparations of 
the day. By R. S. CrisTIANI, Consulting Chemist and Perfumer, 
Philadelphia. 8vo. ; . . . . . $10.00 

COAL AND METAL MINERS' POCKET BOOK: 

Of Principles, Rules, Formulas, and Tables, Specially Compiled 
and Prepared for the Convenient Use of Mine Officials, Mining En- 
gineers, and Students preparing themselves for Certificates of Compe- 
tency as Mine Inspectors or Mine Foremen. Revised and Enlarged 
edition. Illustrated, 565 pages, small l2mo., cloth . $2.00 

Pocket book form, flexible leather with flap . . $2.75 

DAVIDSON. — A Practical Manual of House Paintittg, Grain- 
ing, Marbling, and Sign-Writing: 
Containing full information on the processes of House Painting in 
Oil and Distemper, the Formation of Letters and Practice of Sign- 
Writing, the Principles of Decorative Art, a Course of Elementary 
Drawing for House Painters, Writers, etc., and a Collection of Useful 
Receipts. With nine colored illustrations of Woods and Marbles, 
and numerous wood engravings. By Ellis A. Davidson. i2mo. 

$3.00 

DAVIES. — A Treatise on Earthy and Other Minerals and 
Mining : 
By D. C. Davies, F. G. S„ Mining Engineer, etc. Illustrated by 
76 Engravings. i2mo #5.o<> 



io HENRY CAREY BAIRD & OX'S CATALOGUE. 

DAVXES. — A Treatise on Metalliferous Minerals and Mining: 

By D. C. Davies, F. G. S., Mining Engineer, Examiner of Mir.es. 
Quarries and Collieries. Illustrated by 148 engravings of Geological 
Formations, Mining Operations and Machinery, drawn from the 
practice of all parts of the world. 2d Edition, i2mo., 450 pages $5.00 
DAVIES.— A Treatise on Slate and Slate Quarrying: 

Scientific, Practical and Commercial. By D. C. Davies, F. G. S., 
Mining Engineer, etc. With numerous illustrations and folding 
plates. i3mo #2.03 

DAVIS. — A Treatise on Steam-Boiler Incrustation and Meth- 
ods for Preventing Corrosion and the Formation of Scale .' 
By Charles T. Davis. Illustrated by 65 engravings. 8vo. $1.50 

DAVIS. —The Manufacture of Paper: 

Being a Description of the various Processes for the Fabrication, 
Coloring and Finishing of every kind of Paper, Including the Dif- 
ferent Raw Materials and the Methods for Determining their Values, 
the Tools, Machines and Practical Details connected with an intelli- 
gent and a profitable prosecution of the art, with special reference to 
the best American Practice. To which are added a History of Pa- 
per, complete Lists of Paper-Making Materials, List of American 
Machines, Tools and Processes used in treating the Raw Materials, 
and in Making, Coloring and Finishing Paper. By Charles T. 
Davis. Illustrated by 156 engravings. 608 pages, 8vo. $6.00 

DAVIS.— The Manufacture of Leather: 

Being a description of all of tl Processes for the Tanning, Tawing, 
Currying, Finishing and Dyeing of every kind of Leather ; including 
the various Raw Materials and the Methods for Determining their 
Values; the Tools, Machines, and all Details of Importance con- 
nected with an Intelligent and Profitable Prosecution of the Art, with 
Special Reference to the Best American Practice. To which are 
added Complete Lists of all American Patents for Materials, Pro- 
cesses, Tools, and Machines for Tanning, Currying, etc. By Charles 
Thomas Davis. Illustrated by 302 engravings and 12 Samples of 
Dyed Leathers. One vol., 8vo., 824 pages . . . $io.oa 

DAWIDOWSKY— BRANNT.— A Practical Treatise on the 

Raw Materials and Fabrication of Glue, Gelatine, Gelatine 

Veneers and Foils, Isinglass, Cements, Pastes, Mucilages, 

etc. : 

Based upon Actual Experience. By F. Dawidowsky, Technical 

Chemist. Translated from the German, with extensive additions, 

including a description of the most Recent American Processes, by 

William T. Brannt, Graduate of the Royal Agricultural College 

of Eldena, Prussia. 35 Engravings. l2mo. . . . $2.50 

DE GRAFF.— The Geometrical Stair-Builders' Guide : 

being a Plain Practical System of Hand-Railing, embracing all its 
necessary Details, and Geometrically Illustrated by twenty-two Steel 
Engravings; together with the use of the most approved principles 
of Practical Geometry. By Simon De Graff, Architect. 4to. 

#2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. II 

DE KONINCK— -DIETZ.— A Practical Manual of Chemical 
Analysis and Assaying : 
As applied to the Manufacture of Iron from its Ores, and to Cast Iron, 
"Wrought Iron, and Steel, as found in Commerce. By L. L. De 
Koninck, Dr. Sc, and E. DlETZ, Engineer. Edited with Notes, by 
Robert Mallet, F. R. S., F. S. G., M. I. C. E., etc. American 
Edition, Edited with Notes and an Appendix on Iroc Ores, by A. A. 
Fesquet, Chemist and Engineer. l2mo. . . . $1-5° 

DUNCAN.— Practical Surveyor's Guide: 

Containing the necessary information to make any person of com? 
mon capacity, a finished land surveyor without the aid of a teacher. 
By Andrew Duncan. Revised. 72 engravings, 214pp. i 2m0 - $ I S° 
DUPLAIS. — A Treatise on the Manufacture and Distillation 
of Alcoholic Liquors : 
Comprising Accurate and Complete Details in Regard to Alcohol 
from Wine, Molasses, Beets, Grain, Rice, Potatoes, Sorghum, Aspho ■ 
del, Fruits, etc.; with the Distillation and Rectification of Brandy. 
Whiskey, Rum, Gin, Swiss Absinthe, etc., the Preparation of Aro- 
matic Waters, Volatile Oils or Essences, Sugars, Syrups, Aromatic 
Tinctures, Liqueurs, Cordial Wines, Effervescing Wines, etc., the 
Ageing of Brandy and the improvement of Spirits, with Copiowa 
Directions and Tables for Testing and Reducing Spirituous Liquors, 
etc., etc. Translated and Edited from the French of MM. Dupi.AIS, 
Aine et Jeune. By M. McKennie, M. D. To which are added the 
United States Internal Revenue Regulations for the Assessment and 
Collection of Taxes en Distilled Spirits. Illustrated by fourteen 
folding plates and several wood engravings. 743 pp. 8vo. |io OO 
USSAUCE.— Practical Treatise on the Fabrication of Matches, 
Gun Cotton, and Fulminating Powder. 

By Professor H. Dussauce. i2mo $3 oa 

r-YERAND COLOR-MAKER'S COMPANION: 

Containing upwards of two hundred Receipts for making Colors, on 
the most approved principles, for all the various styles and fabrics now 
in existence; with the Scouring Process, and plain Directions for 
Preparing, Washing-off, and Finishing the Goods. l2mo. $1.00 

EDWARDS.— A Catechism of the Marine Steam-Engine, 

For the use of Engineers, Firemen, and Mechanics. A Practical 
Work for Practical Men. By Emory Edwards, Mechanical Engi- 
neer. Illustrated by sixty-three Engravings, including examples of 
the most modern Engines. Third edition, thoroughly revised,. with 
much additional matter. i2mo. 414 pages ... ^2 00 
EDWARDS. — Modern American Locomotive Engines, 
Their Design, Construction and Management. By Emory Edwards, 
Illustrated i2mo $2.00 

EDWARDS.— The American Steam Engineer: 

Theoretical and Practical, with examples of the latest and most ap- 
proved American practice in the design and construction of Steam 
Engines and Boilers. For the use of engineers, machinists, boiler- 
Wkers, and engineering students. By EMORY Edwards. Fully 
illustrated, 419 pages. i2mo. .... $2.50 



12 HENRY CAREY BAIRD & CO.'S CATALOGUE. 



EDWARDS. — Modern American Marine Engines, Boilers, and 

Screw Propellers, 

Their Design and Construction. Showing the Present Practice of 

the most Eminent Engineers and Marine Engine Builders in the 

United States. Illustrated by 30 large and elaborate plates. 4to. $5.00 

EDWARDS.— The Practical Steam Engineer's Guide 

In the Design, Construction, and Management of American Stationary, 
Portable, and Steam Fire- Engines, Steam Pumps, Boilers, Injectors, 
Governors, Indicators, Pistons and Rings, Safety Valves and Steam 
Gauges. For the use of Engineers, Firemen, and Steam Users. By 
Emory Edwards. Illustrated by 119 engravings. 420 pages. 

I21HO |2 3O 

EISSLER.— The Metallurgy of Gold : 

A Practical Treatise on the Metallurgical Treatment of Gold-Bear- 
ing Ores, including the Processes of Concentration and Chlorination, 
and the Assaying, Melting, and Refining of Gold. By M. Eissler. 

With 132 Illustrations. l2mo. $3-5o 

EISSLER.— The Metallurgy of Silver : 

A Practical Treatise on the Amalgamation, Roasting, and Lixiviation 
of Silver Ores, including the Assaying, Melting, and Refining of 
Silver Bullion. By M. Eissler. 124 Illustrations. 336 pp. 

i2mo . $4.25 

ELDER. — Conversations on the Principal Subjects of Political 
Economy. 
By Dr. William Elder. 8vo $2.50 

ELDER.— Questions of the Day, 

Economic and Social. By Dr. William Elder. 8vo. . $3.00 

ERNI. — Mineralogy Simplified. 

Easy Methods of Determining and Classifying Minerals, including 
Ores, by means of the Blowpipe, and by Humid Chemical Analysis, 
based on Professor von Kobell's Tables for the Determination of 
Minerals, with an Introduction to Modern Chemistry. By HENRY 
Erni, A.M., M.D., Professor of Chemistry. Second Edition, rewritten, 
enlarged and improved. i2mo. . . . . . i?3 oc 

FAIRBAIRN.— The Principles of Mechanism and Machinery 
of Transmission ■ 
Comprising the Principles of Mechanism, W T heels, and Pullevs, 
Strength and Proportions of Shafts, Coupling of Shalts, and Engag- 
ing and Disengaging Gear. By Sir William Fairbairn, Bait 
C. E. Beautifully illustrated by over 1 50 wood-cuts. In one 
volume, i2mo ....... * ■ • #2.50 

FLEMING.— Narrow Gauge Railways in America. 

A Sketch of their Rise, Progress, and Success. Valuable Statistics 
as to Grades, Curves, Weight of Rail, Locomotives, Cars, etc. By 
Howard Fleming. Illustrated, 8vo #1 00 

FORSYTH.— Book of Designs for Headstones, Mural, and 
other Monuments: 
Containing 78 Designs. By James Forsyth. With an Introduction 
ty Charles Bgutell, M. A. 4 to., cloth . . - $5 °° 



HENRY CAREY BAIRD & CO.'S CATALOGUE. *3 



FRANKEL- HOTTER.— A Practical Treatise on the Manu< 
facture of Starch, Glucose, Starch-Sugar, and Dextrine: 
Based on the German of Ladislaus Von Wagner, Professor in the 
Royal Technical High School, Buda-Pest, Hungary, and other 
authorities. By Julius Frankel, Graduate of the Polytechnic 
School of Hanover. Edited by Robert Hutter, Chemist, Practical 
Manufacturer of Starch-Sugar. Illustrated by 58 engravings, cover- 
ing every branch of the subject, including examples of the most 
Recent and Best American Machinery. 8vo., 344 pp. . $3-5° 

uARDNER. — The Painter's Encyclopaedia: 

Containing Definitions of all Important Words in the Art of Plain 
and Artistic Painting, with Details of Practice in Coach, Carriage, 
Railway Car, House, Sign, and Ornamental Painting, including 
Graining, Marbling, Staining, Varnishing, Polishing, Lettering, 
Stenciling, Gilding, Bronzing, etc. By Franklin B. Gardner. 
158 Illustrations. 121110. 427 pp. ..... $2.00 

GARDNER.— Everybody's Paint Book: 

A Complete Guide to the Art of Outdoor and Indoor Painting, De- 
signed for the Special Use of those who wish to do their own work, 
and consisting of Practical Lessons in Plain Painting, Varnishing, 
Polishing, Staining, Pp-orr Hanging, Kalsomining, etc., as well as 
Directions for Renovating Furniture, and Hints on Artistic Work for 
Home Decoration. 38 Illustrations. I2mc, 183 pp. . $1.00 

GEE. — The Goldsmith's Handbook : 

Containing full instructions for the Alloying and Working of Gold, 
including the Art of Alloying, Melting, Reducing, Coloring, Col- 
lecting, and Refining; the Processes of Manipulation, Recovery of 
Waste; Chemical and Physical Properties of Gold; with a New 
System of Mixing its Alloys ; Solders, Enamels, and other Useful 
Rules and Recipes. By George E. Gee. i2mo. . . ^1.75 

GEE.— The Silversmith's Handbook : 

Containing full instructions for the Alloying and Working of Silver, 
including the different modes of Refining and Melting the Metal; its 
Solders ; the Preparation of Imitation Alloys ; Methods of Manipula- 
tion ; Prevention of Waste ; Instructions for Improving and Finishing 
the Surface of the Work ; together with other Useful Information and 
Memoranda. By George E. Gee. Illustrated. i2mo. $1-75 

GOTHIC ALBUM FOR CABINET-MAKERS: 

Designs for Gothic Furniture. Twenty-three plates. Oblong $2.00 

GRANT. — A Handbook on the Teeth of Gears : 

Their Curves, Properties, and Practical Construction. By George 
B. Grant. Illustrated. Third Edition, enlarged. 8vo. $1 00 

GREENWOOD.— Steel and Iron: 

Comprising the Practice and Theory of the Several Methods Pur- 
sued in their Manufacture, and of their Treatment in the Rolling- 
Mills, the Forge, and the Foundry. By William Henry Green- 
wood, F. C. S. With 97 Diagrams, 536 pages. i2mo. #2.00 



14 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

GREGORY.-^— Mathematics for Practical Men : 

Adapted to the Pursuits of Surveyors, Architects, Mechanics, and 
Civil Engineers. By Olinthus Gregory. 8vo., plates $3.00 

GRISWOLD. — Railroad Engineer's Pocket Companion for the 
Field : 
Comprising Rules for Calculating Deflection Distances and Angles, 
Tangential Distances and Angles, and all Necessary Tables for En 
gineers; also the Art of Levelling from Preliminary Survey to the 
Construction of Railroads, intended Expressly for the Young En- 
gineer, together with Numerous Valuable Rules and Examples. By 
W. Griswold. i2mo., tucks $ J -75 

GRUNER. — Studies of Blast Furnace Phenomena: 

By M. L. Gruner, President of the General Council of Mines o5 
France, and lately Professor of Metallurgy at the Ecole des Mines, 
Translated, with the author's sanction, with an Appendix, by L. D. 
B. Gordon, F. R. S. E., F. G. S. Svo. . . . #2.515 

Hand-Book of Useful Tables for the Lumberman, Farmei and 
Mechanic : 
Containing Accurate Tables of Logs Reduced to Inch Board Meas% 
ure, Plank, Scantling and Timber Measure; Wages and Rent, by 
Week or Month; Capacity of Granaries, Bins and Cisterns; Land 
Measure, Interest Tables, with Directions for Finding the Interest on 
any sum at 4, 5, 6, 7 and 8 per cent., and many other Useful Tables. 
32 mo., boards. 186 pages . . . . . . .25 

HASERICK.— The Secrets of the Art of Dyeing Wool, Cotton, 
and Linen, 
Including Bleaching and Coloring Wool and Cotton Hosiery and 
Random Yarns. A Treatise based on Economy and Practice. By 
E. C. Haserick. Illustrated by 323 Dyed Patterns of the Yami 
or Fabrics. 8vo. . . . . . . . . #7.50 

HATS AND FELTING: 

A Practical Treatise on their Manufacture. By a Practical Hatter. 
Illustrated by Drawings of Machinery, etc. 8vo. . . $1.2$ 

HOFFER. — A Practical Treatise on Caoutchouc and Gutta 
Percha, 
Comprising the Properties of the Raw Materials, and the manner or" 
Mixing and Working them ; with the Fabrication of Vulcanized and 
Hard Rubbers, Caoutchouc and Gutta Percha Compositions, Water- 
proof Substances, Elastic Tissues, the Utilization of Waste, etc., etc, 
From the German of Raimund Hoffer. By W. T. BRANNT. 
Illustrated i2mo. ........ $2.50 

HAUPT.— Street Railway Motors: 

With Descriptions and Cost of Plants and Operation of the Various 
Systems now in Use. i2mo. . . . . . $1-75 



HENRY CAREY BAlRD & CO.'S CATALOGUE. t$ 



HAUPT— RHAWN.— A Move for Better Roads : 

Essays on Road-making and Maintenance and Road Laws, for 
which Frizes or Honorable Mention were Awarded through the 
University of Pennsylvania by a Committee of Citizens of Philadel- 
phia, with a Synopsis of other Contributions and a Review by the 
Secretary, Lewis M. Haupt, A. M., C. E.; also an Introduction by 
William H. Rhawn, Chairman of the Committee. 319 pages. 

8vo $ 2 -°° 

HUGHES.— American Miller and Millwright's Assistant: 

By William Carter Hughes. 121110 $1.50 

HULME. — Worked Examination Questions in Plane Geomet- 
rical Drawing : 
For the Use of Candidates for the Royal Military Academy, Wool- 
wich; the Royal Military College, Sandhurst ; the Indian Civil En- 
gineering College, Cooper's Hill ; Indian Public Works and Tele- 
graph Departments ; Royal Marine Light Infantry; the Oxford and 
Cambridge Local Examinations, etc. By F. Edward Hulme, F. L. 
S., F. S. A., Art-Master Marlborough College. Illustrated by 300 
examples. Small quarto ...'.» ° $2.50. 

JER VIS.— Railroad Property: 

A Treatise on the Construction and Management of Railways; 
designed to afford useful knowledge, in the popular style, to the 
holders of this class of property ; as well as Railway Managers, Offi- 
cers, and Agents. By John B. Tervis, late Civil Engineer of the 
Hudson River Railroad,"Croton Aqueduct, etc. i2mo., cloth #2.oc 
KEENE.-A Hand-Book of Practical Gauging: 

For the Use of Beginners, to which is added a Chapter on Distilla- 
tion, describing the process in operation at the Custom- House for 
ascertaining the Strength of Wines. By James B. Keene, of H. M. 

Customs. 8vo. ^' 2 j 

KELLEY.— Speeches, Addresses, and Letters on Industrial and 
Financial Questions : 
By Hon. William D. Kelley, M. C. 544 pages, 8vo. . £2.50 
KELLOGG. — A New Monetary System : 

The only means of Securing the respective Rights of Labor and 
Property, and of Protecting the Public from Financial Revulsions. 
By Edward Kellogg. Revised from his work on "Labor and 
other Capital." With numerous additions from his manuscript. 
Edited by Mary Kellogg Putnam. Fifth edition. To which is 
added a Biographical Sketch of the Author. One volume, I2mc>. 

Paper cover $ 100 

Bound in cloth ^S 

KEMLO.— Watch-Repairer's Hand-Book : 
Beino- a Complete Guide to the Young Beginner, in Taking Apart, 
Putting Together, and Thoroughly Cleaning the English Lever and 
other Foreign Watches, and all American Watches. By F. Kemlo, 
Practical Watchmaker. With Illustrations. i2mo. . $1-2$ 



16 HENRY CARCY BAIRD & CO.'S CATALOGUE. 

KENTISH.— A Treatise on a Box of Instruments, 

And the Slide Rule ; with the Theory of Trigonometry and Log* 
lirhms, including Practical Geometry, Surveying, Measuring of Tim- 
ber, Cask and Malt Gauging, Heights, and Distances. By Thomas 
Kentish. In one volume. i2mo. .... $1.2 

KERL. — The Assayer's Manual: 

An Abridged Treatise on the Docimastic Examination of Ores, and 
Furnace and other Artificial Products. By Bruno Kerl, Professor 
in the Royal School of Mines. Translated from the German by 
William T. BrannT. Second American edition, edited with Ex- 
tensive Additions by F. LynWood GARRISON, Member of the 
American Institute of Mining Engineers, etc. Illustrated by 87 en- 
gravings. 8vo $3-00 

KICK.— Flour Manufacture. 

A Treatise on Milling Science and Practice. By FREDERICK Kick, 
Imperial Regierungsrnth, Professor of Mechanical Technology in the 
imperial German Polytechnic Institute, Prague. Translated from 
the second enlarged and revised edition with supplement by H. H. 
P. Powles, Assoc. Memb Institution of Civil Engineers. Illustrated 
with 28 Plates, and 167 Wood-cuts. 367 pages. 8vo. . #10.07 

KINGZETT.— The History, Products, and Processes of the 
Alkali Trade : 
Including the most Recent Improvements. By Charles Thomas 
Kingzett, Consulting Chemist. With 23 illustrations. 8vo. #2.50 

KIRK.— The Founding of Metals: 

A Practical Treatise on the Melting of Tron, with a Description of the 
Founding of Alloys; also, of all the Metals and Mineral Substance* 
used in the Art of Founding. Collected from original sources. By 
Edward Kirk, Practical Foundryman and Chemist. Illustrated. 
Third editon. 8vo. . . . .-.-'. . . $2.$Q 

LANDRIN.— A Treatise on Steel: 

Comprising its Theory, Metallurgy, Properties, Practical Working, 
and Use. By M. H. C. Landrin, Jr., Civil Engineer. Translated 
from the French, with Notes, by A. A. Fesquet, Chemist and En- 
gineer. With an Appendix on the Bessemer and the Martin Pre- 
rp«ses for Manufacturing Steel, from the Report of Abram S. Hewitt? 
United States Commissioner to the Universal Exposition, Paris, 1867.* 
12mo $3.00 

LANGBEIN. — A Complete Treatise on the Electro-Deposition 
of Metals : 
Translated from the German, with Additions, by Wm, T. Brannt. 
125 illustrations. 8vo. . . . . . . , #4.00 

LARDNER.— The Steam-Engine : 

For the Use of Beginners. Illustrated. 121110. . . . 75 

LEHNER.— The Manufacture of Ink: 

Comprising the Raw Materials, and the Preparation of Writing, 
Copying and Hektograph Inks, Safety Inks, Ink Extracts and Pow- 
ders, etc. Translated from the German of SlGMUND Lehner, with 
additions by William T. Brannt. Illustrated. i2mo. #2.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 17 

LARKIN. — The Practical Brass and Iron Founder's Guide; 

A Concise Treatise on Brass Founding, Moulding, the Metals and 
their Alloys, etc.; to which are added Recent Improvements in the 
Manufacture of Iron, Steel by the Bessemer Process, etc., etc. By 
James Larkin, late Conductor of the Brass Foundry Department it; 
Reany, Neafie & Co.'s Penn Works, Philadelphia. New edition, 
revised, with extensive additions. l2mo. . . . $2.50 

LEROUX. — A Practical Treatise on the Manufacture of 
Worsteds and Carded Yarns : 
Comprising Practical Mechanics, with Rules and Calculations applied 
to Spinning; Sorting, Cleaning, and Scouring Wools; the English 
and French Methods of Combing, Drawing, and Spinning Worsteds, 
and Manufacturing Carded Yarns. Translated from the French of 
CHARLES Leroux, Mechanical Engineer and Superintendent of a 
Spinning Mill, by Horatio Paine, M. D., and A. A. Fesquet, 
Chemist and Engineer. Illustrated by twelve large Plates. To which 
is added an Appendix, containing Extracts from the Reports of the 
International Jury, and of the Artisans selected by the Committee 
appointed by the Council of the Society of Arts, London, on. Woolen 
and Worsted Machinery and Fabrics, as exhibited in the Paris Uni- 
versal Exposition, 1867. 8vo. ..... $5.00 

LEFFEL.— The Construction of Mill-Dams : 
Comprising also the Birlding of Race and Reservoir Embankments 
and Head-Gates, the Measurement of Streams, Gauging ' of Water 
Supply, etc. By James Leffel & Co. Illustrated by 58 engravings. 
8vo. $2.50 

LESLIE.— Complete Cookery: 
Directions for Cookery in its Various Branches. By Miss Leslie. 
Sixtieth thousand. Thoroughly revised, with the addition of New 
Receipts. i2mo $1.50 

LE VAN. — The Steam Engine and the Indicator : 

Their Origin and Progressive Development ; including the Most 
Recent Examples of Steam and Gas Motors, together with the Indi- 
cator, its Principles, its Utility, and its Application. By William 
Barnet Le Van. Illustrated by 205 Engravings, chiefly of Indi- 
cator-Cards. 469 pp. 8vo. $4-oo 

LIEBER.— Assayer's Guide : 
Or, Fractical Directions to Assayers, Miners, and Smelters, for the 
Tests and Assays, by Heat and by Wet Processes, for the Ores of all 
the principal Metals, of Gold and Silver Coins and Alloys, and of 
Coal, etc. By Oscar M. Lieber. Revised. 283 pp. limo. #1.50 

iLockwood's Dictionary of Terms : 

Used in the Practice of Mechanical Engineering, embracing thos-e 
Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turn- 
ing, Smith's and Boiler Shops, etc., etc., comprising upwards of Six* 
Thousand Definitions. Edited by a Foreman Pattern Maker, author 
<4 " Pattern Making." 417 pp. l2mo. . . . #3-°° 



18 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

LUKIN. — Amongst Machines: 

Embracing Descriptions of the various Mechanical Appliances used 
in the Manufacture of Wood, Metai, and other Substances. J2mo. 

#1-75 
LUKIN.— The Boy Engineers: 

What They Did, and How They Did It. With" 30 plates. l8mo. 

LUKIN.— The Young Mechanic : 

Practical Carpentry. Containing Directions for the Use of all kinds 
of Tools, and for Construction of Steam-Engines and Mechanical 
Models, including the Art of Turning in Wood and Metal. By John 
LUKIN, Author of "The Lathe and Its Uses," etc. Illustrated. 
i2mo $i-75 

MAIN and BROWN. — Questions on Subjects Connected with 

the Marine Steam-Engine : 

And Examination Papers; with Hints for their Solution. By 

Thomas J. Main, Professor of Mathematics, Royal "tfaval College, 

and Thomas Brown, Chief Engineer, R. N. i2mo., cloth. $1.00 

MAIN and BROWN. — The Indicator and Dynamometer: 
With their Practical Applications to the Steam-Engine. By THOMAS 
J. Main, M. A. F. R., Ass't S. Professor Royal Naval College, 
Portsmouth, and Thomas Brown, Assoc. Inst. C. E., Chief Engineer 
R. N., attached to the R. N. College. Illustrated. 8vo. . $1.00 

MAIN and BROWN.— The Marine Steam-Engine. 

By Thomas J. Main, F. R. Ass't S. Mathematical Professor at the 
Royal Naval College, Portsmouth, and Thomas Brown, Assoc. 
Inst. C. E., Chief Engineer R. N. Attached to the Royal Naval 
College. With numerous illustrations. 8vo. 

MAKINS.— A Manual of Metallurgy: 

By George Hogarth Makins. 100 engravings. Second edition 
rewritten and much enlarged. i2mo., 592 pages . . $3-O0 

MARTIN.— Screw- Cutting Tables, for the Use of Mechanical 
Engineers : 
Showing the Proper Arrangement of Wheels for Cutting the Threads 
of Screws of any Required Pitch ; with a Table for Making the Uni- 
versal Gas-Pipe Thread and Taps. By W. A. Martin, Engineer. 
8vo. 50 

MICHELL.— Mine Drainage: 
Being a Complete and Practical Treatise on Direct-Acting Under. 
jrround Steam Pumping Machinery. With a Description of a large 
number of the best known Engines, their General Utility and ihe 
n Special Sphere of their Action, the Mode of their Application, and 
their Merits compared with other Pumping Machinery. By STEPHEN 
MlCHELL. Illustrated by 137 engravings. 8vo., 277 pages . #6.00 

MOLESWORTH.— Pocket-Book of Useful Formulae and' 

Memoranda for Civil and Mechanical Engineers. 

By Guilford L. Molesworth, Member of the Institution of Civil 

Engineers, Chief Resident Engineer of the Ceylon Railway. Full- 

bound in PGcket-book form . . . • > • £i.ot 



HENRY CAREY BAJ.RD & CO.*S CATALOGUE. 19 

MOORE. — The Universal Assistant and the Complete Me- 
chanic : 

Containing over one million Industrial Facts, Calculations, Receipts, 
Processes, Trades Secrets, Rules, Business Forms, Legal Items, Etc., 
in every occupation, from the Household to the Manufactory. By 
R. Moore. Illustrated by 500 Engravings. i2mo. . $2.50 

MORRIS. — Easy Rules for the Measurement of Earthworks; 
By means of the Prismoidal Formula. Illustrated with Numerous 
Wood-Cuts, Problems, and Examples, and concluded by an Exten- 
sive Table for finding the Solidity in cubic yards from Mean Areas. 
The whole being adapted for convenient use by Engineers, Surveyors, 
Centractors, and others needing Correct Measurements of Earthwork. 
By Elwood Morris, C. E. 8vo $1.50 

MAUCHLINE.— The Mine Foreman's Hand-Book 

Of Practical and Theoretical Information on the Opening, Venti- 
lating, and Working of Collieries. Questions and Answers on Prac- 
tical and Theoretical Coal Mining. Designed to Assist Students and 
Others in Passing Examinations for Mine Foremanships. By 
Robert Mauchline, Ex-Inspector of Mines. A New, Revised and 
Enlarged Edition. Illustrated by 114 engravings. 8vo. 337 
pages #375 

NAPIER. — A System of Chemistry Applied to Dyeing. 

By James Napier, F. C. S. A New and Thoroughly Revised Edi- 
tion. Completely brought up to the present state of the Science, 
including the Chemistry of Coal Tar 'Colors, by A. A. Fesquet, 
Chemist and Engineer. With an Appendix on Dyeing and Calico 
Printing, as shown at the Universal Exposition, Paris, 1867. Illus- 
trated. 8vo. 422 pages . . . . . . . $3-5o 

NEVILLE.— Hydraulic Tables, Coefficients, and Formulae, for 
finding the Discharge of Water from Orifices, Notches, 
Weirs, Pipes, and Rivers : 
Third Edition, with Additions, consisting of New Formulae for the 
Discharge from Tidal and Flood Sluices and Siphons ; general infor- 
mation on Rainfall, Catchment-Basins, Drainage, Sewerage, Water 
Supply for Towns and Mill Power. By Tohn Neville, C. E. M. R. 
I. A. ; Fellow of the Royal Geological Society of Ireland. Thicli 
l2mo $5-5° 

NEWBERY. — Gleanings from Ornamental Art of every 
style : 
Drawn from Examples in the British, South Kensington, Indian, 
Crystal Palace, and other Museums, the Exhibitions of 185 1 and 
1862, and the best Engiish and Foreign works. In a. series of IOQ 
exquisitely drawn Plates, containing many hundred examples. Bjf 
Robert Newbery. 4to. $12.50 

NICHOLLS. —The Theoretical and Practical Boiler-Maker and 
Engineer's Reference Book: 
Containing a variety of Useful Information for Employers of Labor- 
Foremen and Working Boiler- Makers, Iron, Copper, and Tinsmith* 



20 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

.Draughtsmen, Engineers, the General Steam-using Public, and for thfl 
Use of Science Schools and Classes. By Samuel Nicholas. Illu* 
trated by sixteen plaies, iamo. ..... $2.$Q 

NICHOLSON.— A Manual of the Art of Bookbinding: 

Containing full instructions in the different Branches of Forwarding, 
Gilding, and Finishing. Also, the Art of Marbling Book-edges and 
Paper. By James B. Nicholson. Illustrated. i2mo., cloth $2.25 

NICOLLS.— The Railway Builder: 
A Hand-Book for Estimating the Probable Cost of American Rail* 
way Construction and Equipment. By WILLIAM J. NlCOLLS, Civil 
Engineer. Illustrated, full bound, pocket-book form . $2.00 

NORMANDY.— The Commercial Handbook of Chemical An- 
alysis : 
Or Practical Instructions for the Determination of the Intrinsic o* 
Commercial Value of Substances used in Manufactures, in Trades, 
and in the Arts. By A. Normandy. New Edition, Enlarged, and 
to a great extent rewritten. By Henry M. Noad, Ph.D., F.R.S., 
thick l2mo. $5.00 

NORRIS. — A Handbook for Locomotive Engineers and Ma- 
chinists : 
Comprising the Proportions and Calculations for Constructing Loco- 
motives; Manner of Setting Valves; Tables cf Squares, Cubes, Areas, 
etc., etc. By Septimus Norris, M. E. New edition. Illustrated, 
I2mo $1.50 

NYSTROM. — A New Treatise on Elements of Mechanics : 
Establishing Strict Precision in the Meaning of Dynamical Terms: 
accompanied with an Appendix on Duodenal Arithmetic and Me- 
trology. By John W. Nystrom, C. E. Illustrated. 8vo. $2.00 

NYSTROM. — On Technological Education and the Construc- 
tion of Ships and Screw Propellers : 
For Naval and Marine Engineers. By John W. NystroM, lata 
Acting Chief Engineer, U. S/N. Second edition, revised, with addi- 
tional matter. Illustrated by seven engravings. i2mo. . $1.50 

O'NEILL. — A Dictionary of Dyeing and Calico Printing: 

Containing a brief account of all the Substances and Processes in 
use in the Art of Dyeing and Printing Textile Fabrics ; with Practical 
Receipts and Scientific Information. By Charles O'Neill, Analy- 
tical Chemist. To which is added an Essay on Coal Tar Colors and 
their application to Dyeing and Calico Printing. By A. A. Ff.SQUET, 
Chemist and Engineer. With an appendix on Dyeing and Calico 
Printing, as shown at the Universal Exposition, Paris, 1867- 8vo., 
491 pages $ 3 . 5 o 

ORTON. — Underground Treasures 1 . 

How and Where to P'ind Them. A Key for the Ready Determination 
of ail the Useful Minerals within the United States. By James 
ORTON, A.M., Late Professor of Natural History in Vassar College, 
fi. Y.; Cor. Mem. of the Academy of Natural Sciences, Philadelphia, 
and of the Lyceum of Natural History, New York ; author of the 
''Andes and the Amazon," etc. A New Edition, with Additions. 
Illustrated »>••...,*. $i.$9 



HENRY CAREY BAiRD & CO.'S CATALOGUE. 21 



OSBORN. — The Prospector's Field Book and Guide : 

In the Search for and the Easy Determination of Ores and Other 
Useful Minerals. By Prof. H. S. OsBORN, LL. D., Author of 
"The Metallurgy of Iron and Steel;" "A Practical Manual of 
Minerals, Mines, and Mining." Illustrated by 44 Engravings. 

l2mo $l-5o 

OSBORN. — A Practical Manual of Minerals, Mines and Min- 

in = : 
Comprising the Physical Properties, Geologic Positions, Local Occur- 
rence and Associations of the Useful Minerals; their Methods of 
Chemical Analysis and Assay: together with Various Systems of 
Excavating and Timbering, Buck and Masonry Work, during Driv- 
ing, Lining, Bracing and other Operations, etc. By Prof. H. S. 
Osborn, LL. D., Author of the " Metallurgy of Iron and Steel." 
Illustrated by 171 engravings from original drawings. 8vo. #4.50 

OVERMAN.— Tin; Manufacture of Steel : 

Containing the Practice and Principles of Working and Making Steel. 
A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon 
Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard- 
ware, of Steel and Iron, and for Men of Science and Art. By 
Frederick Overman, Mining Engineer, Author of the " Manu- 
facture of Lon," etc. A new, enlarged, and revised Edition. By 
A. A. Fesql.«£T, Chemist and Engineer. i2mo. . . $1.50 

OVERMAN.— The Moulder's and Founder's Pocket Guide : 
A Treatise on Moulding and Founding in Green-sand, Dry-sand, Loam, 
and Cement; the Moulding of Machine Frames, Mill-gear, Hollow- 
ware, Ornaments, Trinkets, Bells, and Statues; Description of Moulds 
for Iron, Brcnze, Brass, and other Metals; Plaster of Paris, Sulphur, 
Wax, etc. ; the Construction of Melting Furnaces, the Melting and 
Founding of Metals ; the Composition of Alloys and their Nature, 
etc., etc. By Frederick Overman, M. E. A new Edition, to 
which is added a Supplement on Statuary and Ornamental Moulding, 
Ordnance, Malleable Iron Castings, etc. By A. A. FESQUET, Chem- 
ist and Engineer. Illustrated bv 44 engravings. l2mo. . $2.O0, 

PAINTER, GILDER, AND VARNISHER'S COMPANION/ 
Containing Rules and Regulations in everything relating to the AriS 
of Painting, Gilding, Varnishing, Glass-Staining, Graining, Marbling, 
Sign- Writing, Gilding on Glass, and Coach Painting and Varnishing; 
Tests for the Detection of Adulterations in Oils, Colors, etc.; and a 
Statement of the Diseases to which Painters are peculiarly liable, with 
the Simplest and Best Remedies. Sixteenth Edition. Revised, with 
an Appendix. Containing Colors and Coloring — Theoretical ana 
Practical. Comprising descriptions of a great variety of Additional 
Pigments, their Qualities and Uses, to which are added, Dryers, and 
Modes and Operations of Painting, etc. Together with Chevreul*s 
Principles of Harmony and Contrast of Colors. i2mo. Cloth $1.5^ 

SPALLETT.— The Miller's, Millwright's, and Engineer's Guide. 
By Henry Pallett. Illustrated. i2mo. . . » #2.oq 



22 KENRY CAREY BAIRD & CO.'S CATALOGUE. 

PERCY.— The Manufacture of Russian Sheet-Iron. 

By John Percy, M. D., F. R. S., Lecturer on Metallurgy at the 
Royal School of Mines, and to The Advance Class of Artillery 
Officers at the Royal Artillery Institution, Woolwich; Author of 
"Metallurgy." With Illustrations. 8vo., paper . . 50 cts. 

PERKINS.— Gas and Ventilation : 

Practical Treatise on Gas and Ventilation. With Special Relation 
to Illuminating, Heating, and Cooking by Gas. Including Scientific 
Helps to Engineer-students and others. With Illustrated Diagrams, 
By E. E. Perkins. i2mo., cloth $1.25 

PERKINS AND STOWE.-A New Guide to the Sheet-iron 
and Boiler Plate Roller : 
Containing a Series of Tables showing the Weight of Slabs and Piles 
to Produce Boiler Plates, and of the Weight of Piles and the Sizes of 
Bars to produce Sheet-iron ; the Thickness of the Bar Gauge 
in decimals; the Weight per foot, and the Thickness on the Bar or 
Wire Gauge of the fractional parts of an inch; the Weight per 
sheet, and the Thickness on the Wire Gauge of Sheet-iron of various 
dimensions to weigh 112 lbs. per bundle; and the conversion of 
Short Weight into Long Weight, and Long Weight into Short. 
Estimated and collected by G. H. Perkins and J. G- Stowe. $2.50 

POWELL— CHANCE— HARRIS,— The Principles of Glass 

Making. 

By Harry J. Powell, B. A. Together with Treatises on Crown and 

Sheet Glass; by Henry Chance, M. A. And Plate Glass, by H. 

G. Harris, Asso. M. Inst. C. E. Illustrated i8mo. . $i-S Q 

PROCTOR.— A Pocket-Book of Useful Tables and Formula 
for Marine Engineers : 
By Frank Proctor. Second Edition, Revised and Enlarged. 
Full -bound pocket-book form ...... $1.50 

REGNAULT.— Elements of Chemistry: 
By M. V. Regnault. Translated from the French by T. Forrest 
Betton, M. D., and edited, with Notes, by James C. Booth, Melter 
and Refiner U. S. Mint, and William L. Fab'ER, Metallurgist and 
Mining Engineer. Illustrated by nearly 700 wood-engravings. Com- 
prising nearly 1,500 pages. In two volumes, 8vo., cloth . $ 7 -50 

RICHARDS.— Aluminium : 

Its History, Occurrence, Properties, Metallurgy and Applications, 
including its Alloys. By Joseph W. Richards, A. C, Chemist and 
Practical Metallurgist, Member of the Deutsche Chemische Gesell- 
schaft. Illustrated ........ #5.00 

RIFFAULT, VERGNAUD, and TOUSSAINT.— A Practical 
Treatise on the Manufacture of Colors for Painting : 
Comprising the Origin, Definition, and Classification of Colors: the 
Treatment of the Raw Materials ; the best Formulae and the Newest 
Processes for the Preparation of every description of Pigment, and 
the Necessary Apparatus and Directions for its Use; Dryers; the 
Testing. Application, and Qualities of Paints, etc., etc. By MM. 
RiFKA'JLT, Yergnaud, and Toussaikt. Revised and Edited by M. 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 23 

F. Malepeyre. Tran&lated from the French, by A. A. FesquSI^ 
Chemist and Engineer. Illustrated by Eighty engravings. In one 
vol., 8vo., 659 pages $75Q 

ROPER. — A Catechism of High-Pressure, or Non-Condensing 
Steam-Engines : 
Including the Modelling, Constructing, and Management of Steam- 
Engines and Steam Boilers. With valuable illustrations. By Ste- 
phen Roper, Engineer. Sixteenth edition, revised and enlarged. 
i8mo., tucks, gilt edge ....... $2.oa 

ROPER.— Engineer's Handy-Book: 

Containing a full Explanation of the Steam-Engine Indicator, and its 
Use and Advantages to Engineers and Steam Users, With Formula 
/or Estimating the Power of all Classes of Steam-Engines; also, 
Facts, Figures, Questions, and Tables for Engineers who wish to 
qualify themselves for the United States Navy, the Revenue Service, 
the Mercantile Marine, or to take charge of the Better Class of Sta- 
tionary Steam-Engines. Sixth edition. l6mo., 690 pages, tucks, 
gilt edge . $3.50 

ROPER. — Hand-Book of Land and Marine Engines : 

Including the Modelling, Construction, Running, and Management 
of Land and Marine Engines and Boilers. With illustrations. By 
Stephen Roper, Engineer. Sixth edition. i2mo., ticks, gilt edge. 

$3-50 
ROPER.— Hand-Book of the Locomotive : 

Including the Construction of Engines and Boilers, and the Construc- 
tion, Management, and Running of Locomotives. By Stephen 
Roper. Eleventh edition. i8mo., tucks, gilt edge . $2.50 

ROPER.— Hand-Book of Modern Steam Fire- Engines. 

With illustrations. By Stephen Roper, Engineer. Fourth edition, 
l2mo., tucks, gilt edge ....... $3.50 

ROPER. — Questions and Answers for Engineers. 

This little book contains all the Questions that Engineers will be 
asked when undergoing an Examination for the purpose of procuring 
Licenses, and they are so plain that any Engineer or Fireman of or ' 
dinary intelligence may commit them to memory in a short time. By 
Stephen Roper, Engineer. Third edition . . . $3.00 

ROPER.— Use and Abuse of the Steam Boiler. 

By Stephen Roper, Engineer. Eighth edition, with illustrations. 
l8mo., tucks, gilt edge . . . . . . $2.00 

ROSE. — The Complete Practical Machinist : 

Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and 
Dies, Hardening and Tempering, the Making and Use of Tools, 
Tool Grinding, Marking out Work, etc. By Joshua Rose. Illus* 
trated by 356 engravings. Thirteenth edition, thoroughly revised 
and in great part rewritten. In one vol., i2mo., 439 pages $2.50" 

ROSE.— Mechanical Drawing Self-Taught: 
Comprising Instructions in the Selection and Preparation of Drawing 
Instruments, Elementary Instruction in Practical Mechanical Draw 



24 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

_____ V 

ing, together with Examples in Simple Geometry and Elementary 
Mechanism, including Screw Threads, Gear Wheels, Mechanical 
Motions, Engines and Boilers. By Joshua Rose, M. E. Illustrated 
by 330 engravings. 8vo , 313 pages ' . . . . $4.00 

ROSE.— The Slide- Valve Practically Explained: 

Embracing simple and complete Practical Demonstrations of th. 
operation of each element in a Slide-valve Movement, and illustrat- 
ing the effects of Variations in their Proportions by examples care- 
fully selected from the most recent and successful practice. By 
Joshua Rose, M. E. Illustrated by 35 engravings . $1.00 

ROSS. — The Blowpipe in Chemistry, Mineralogy and Geology: 
Containing all Known Methods of Anhydrous Analysis, many Work- 
ing Examples, and Instructions for Making Apparatus. By Lieut. - 
Colonel W. A. Ross, R. A., F. G. S. With 120 Illustrations. 
i2mo. .......... $2.00 

SHAW.— Civil Architecture : 

Being a Complete Theoretical and Practical System of Building, con- 
taining the Fundamental Principles of the Art. By Edward Shaw, 
Architect. To which is added a Treatise on Gothic Architecture, etc. 
By Thomas W. Silloway and George M. Harding, Architects. 
The whole illustrated by 102 quarto plates finely engraved on copper. 
Eleventh edition. 4to. ....... $10.00 

SHUNK. — A Practical Treatise on Railway Curves and Loca- 
tion, for Young Engineers. 

By W. F. Shunk, C. E. 121110. Full bound pocket-book form $2.00 

SLATER.— The Manual of Colors and Dye Wares. 

By J. W. Slater. i2mo #3.00 

SLOAN. — American Houses: 

A variety of Original Designs for Rural Buildings. Illustrated by 
26 colored engravings, with descriptive references. By Samuel 
Sloan, Architect. 8vo. $1.50 

SLOAN. — Homestead Architecture : 

Containing Forty Designs for Villas, Cottages, and Farm-houses, with 
Essays on Sty.-., Construction, Landscape Gardening, Furniture, etc., 
etc. T'lustrated by upwards of 200 engravings. By Samuel Sloan, 
Architect. 8vo. . . ' , . . . . $3.50 

SLOANE. — Ho,re Experiments m Science. 

By T. O'Conor Slcane, E. M., A.M., Ph.D. Illustrated by 91 
engravings. i2mo. ....... #1.50 

SMEATON- Builder's Pockt.-Companion : 

Containing the Elements of Building, Surveying, and Architecture; 

with Practical Rules and Instructions co.-^ected with the subject. 
' By A. C. Smeaton, Civil Engineer, etc. i2mo. . . $1.53 
SMITH.— A Manual of Political Economy. 

By E. Peshine Smith. A New Edition, to which is added a full 

Index. i2mo, . . $1 25 



HENRY CAREY EAIRD & CO.'S CATALOGUE. 25 

SMITH. — Parks and Pleasure- Grounds : 

Or Practical Notes on Country Residences, Villas, Public Parks, and 
Gardens. By Charles H. J. Smith, Landscape Gardener and 
Garden Architect, etc., etc. 121110. .... $2.00 

SMITH.— The Dyer's Instructor: 

Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, 
Wool, and Worsted, and Woolen Goods; containing nearly 80a 
Receipts. To which is added a Treatise on the Art of Padding; and 
the Printing of Silk Warps, Skeins, and Handkerchiefs, and the 
various Mordants and Colors for the different styles of such work. 
By David Smith, Pattern Dyer. 121110. . . . $2.00 

SMYTH. — A Rudimentary Treatise on Coal and Coal-Mining. 
By Warrington W. Smyth, M. A., F. R. G., President R. G. S, 
of Cornwall. Fifth edition, revised and corrected. With numer- 
ous illustrations. 121110. . . . . . . $1.7$ 

SNIVELY. — Tables for Systematic Qualitative Chemical Anak 
ysis. 
By John H. Snively, Phr. D. 8vo. . . . . $1.00 

SNIVELY.— The Elements of Systematic Qualitative Chemical 
Analysis : 
A Hand-book for Beginners. By John H. Snively, Phr. D. i6mo. 

$2.oa 

STOKES. — The Cabinet Maker and Upholsterer's Companion: 
Comprising the Art of Drawing, as applicable to Cabinet Work; 
Veneering, Inlaying, and Buhl-Work; the Art of Dyeing and Stain- 
ing Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacker- 
ing, Japanning, and Varnishing; to make French Polish, Glues, 
Cements, and Compos'.:- ns; with numerous Receipts, useful to work 
men generally. Bv Stokes. Illustrated. A New Edition, with 
an Appendix upor /ench Polishing, Staining, Imitating, Varnishing, 
etc., etc. i2mo . . #l.2« 

STRENGTH AND OTHER PROPERTIES OF METALS; 
Reports of Experiments on the Strength and other Properties of 
Metals for Cannon. With a Description of the Machines for Testing 
Metals, and of the Classification of Cannon in service. By Officers 
of the Ordnance Department, U. S. Army. By authority of the Secre- 
tary of War. Illustrated by 25 large steel plates. Quarto . $io.oq 

SULLIVAN. — Protection to Native Industry. 
By Sir Edward Sullivan, Baronet, author of " Ten Chapters on 
Social Reforms." 8vo. ....... $1.00 

SULZ. — A Treatise on Beverages : 

Or the Complete Practical Bottler. Full instructions for Laboratory 
Work, with Original Practical P.ecipes for all kinds of Carbonated 
Drinks, Mineral Waters, Flavorings. Extracts, Syrups, etc. By 
Chas Herman Sulz. Tecbhical Chemist ana Practical Bottler 
Illustrated by 428 Engravings. 8i<* ipp. 5$vQ . . #10.00 



26 HENRY CAREY BAIRl? & CO.'S CATALOGUE. 



SYME. — Outlines of an Industrial Science. 

By David Syme. i2mo. . . ... $2.oa 

TABLES SHOWING THE WEIGHT OF ROUND, 
SQUARE, AND FLAT BAR IRON, STEEL, ETC., 
By Measurement. Cloth ...... 63 

TAYLOR.— Statistics of Coal : 

Including Mineral Bituminous Substances employed in Arts and 
Manufactures; with their Geographical, Geological, and Commercial 
Distribution and Amount of Production and Consumption on the 
American Continent. With Incidental Statistics of the Iron Manu- 
facture. By R. C. Taylor. Second edition, revised by S. S. Halde- 
man. Illustrated by five Maps and many wood engravings. 8vo., 
cloth $10.00 

TEMPLETON. — The Practical Examinator on Steam and the 
Steam -Engine : 
With Instructive References relative thereto, arranged for the Use o? 
Engineers, Students, and others. By William Templeton, En- 
gineer. i2mo. ........ $1.00 

THAUSING.— The Theory and Practice of the Preparation of 
Malt and the Fabrication of Beer: 
With especial reference to the Vienna Process of Brewing. Elab- 
orated from personal experience by Julius E. Thausing, Professor 
at the School for Brewers, and at the Agricultural Institute, Modling, 
near Vienna. Translated from the German by William T. Brannt, 
Thoroughly and elaborately edited, with much American matter, and 
according to the latest and most Scientific Practice, by A. Schwarz 
and Dr. A. H. Bauer. Illustrated by 140 Engravings. 8vo., 815 
pages .......... $10.00 

THOMAS. — The Modern Practice of Photography: 

By R. W. Thomas, F. C. S. 8vo. .... 25 

THOMPSON.— Political Economy. With Especial Reference 
to the Industrial History of Nations : 
By Robert E. Thompson, M. A., Professor of Social Science in the 
University of Pennsylvania. i2mo. .... $1.50 

THOMSON.— Freight Charges Calculator: 

By Andrew Thomson, Freight Agent. 2q.mo. . . $1.25 

TURNER'S (THE) COMPANION: 

Containing Instructions in Concentric, Elliptic, and Eccentric Turn-, 
hig; also various Plates of Chucks, Tools, and Instruments; and 
Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and 
Circular Rest; with Patterns and Instructions for working them 
I2mo $125 

TURNING : Specimens of Fancy Turning Executed on the 
Hand or Foot-Lathe : 
With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting 
Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 

. 4to $3.00 



HEKRY CAREY BA1RB & CO.'S CATALOGUE. 27 

VAILE. — Galvanized-Iron Cornice-Worker's Manual : 

Containing Instructions in Laying out the Different Mitres, and 
Making Patterns for all kinds of Plain and Circular Work. Also, 
Tables of Weights, Areas, and Circumferences of Circles, and other 
Matter calculated to Benefit the Trade. By CHARLES A. Vaile. 
Illustrated by twenty-one plates. 4to $5-°° 

VILLE. — On Artificial Manures : 

Their Chemical Selection and Scientific Application to Agriculture. 
A series of Lectures given at the Experimental Farm at Vincennes, 
during 1867 and 1874-75. By M. Georges Ville. Translated and 
Edited by W 7 illiam Crookes, F. R. S. Illustrated by thirty-one 

engravings. 8vo., 450 pages $6.00 

VILLE.— The School of Chemical Manures : 

Or, Elementary Principles in the Use of Fertilizing Agents. From 
the French of M. Geo. Ville, by A. A. Fesquet, Chemist and En- 
gineer. With Illustrations. i2mo. .... $1.25 

VOGDES. The Architect's and Builder's Pocket- Companion 

and Price-Book : 
Consisting of a Shoit but Comprehensive Epitome of Decimals, Duo- 
decimals, Geometry and Mensuration ; with Tables of United States 
Measures, Sizes, Weights, Strengths, etc., of Iron, Wood, Stone, 
.Brick, Cement and Concretes, Quantities of Materials in given Sizes 
and Dimensions of Wood, Brick and Stone; and full and complete 
Bibs of Prices for Carpenter's Work and Painting; also, Rules for 
Computing and Valuing Brick and Brick Work, Stone Work, Paint- 
tnCT, Plastering, with a Vocabulary of Technical Terms, etc. By 
FRANK VV. Vogdes, Architect, Indianapolis, Ind. Enlarged, revised, 
and corrected. In one volume, 368 pages, full-bound, pocket-book 

form, gilt edges $2.00 

Cloth . l-5« 

VAN CLEVE. — The English and American Mechanic: 

Comprising a Collection of Over Three Thousand Receipts, Rules, 
and Tables, designed for the Use of every Mechanic and Manufac- 
turer. By B. Frank Van Cleve. Illustrated. 500 pp. umo. $2.00 
WAHNSCHAFFE.— A Guide to the Scientific Examination 
of Soils : 
Comprising Select Methods of Mechanical and Chemical Analysis 
and Physical Investigation. Translated from the German of Dr. F. 
Wahnschafke. With additions by William T. Brannt. Illus- 
trated by 25 engravings. 121110. 177 pages . . • $1-5^ 

WALL. — Practical Graining : 

With Descriptions of Colors Employed and Tools Used. Illustrated 
by 47 Colored Plates, Representing the Various Woods Used t 
Interior Finishing. By William E. Wall. 8vo. . #2.5? 

WALTON. — Coal-Mining Described and Illustrated: 

By Thomas H. Walton, Mining Engineer. Illustrated by 24 large 
and elaborate Plates, after Actual Workings and Apparatus. #5.06, 



2S HENRY CAREY BAIRD & CO.'S CATALOGUE. 

WARE.— The Sugar Beet. 

Including a History of the Beet Sugar Industry in Europe, Varietier 
of the Sugar Beet, Examination, Soils, Tillage, Seeds and Sowings 
Yield and Cost of Cultivation, Harvesting, Transportation, Conserva 
tion, Feeding Qualities of the Beet and of the Pulp, etc. By Lewis 
S. Ware, C. E., M. E. Illustrated by ninety engravings. 8vo. 

WARN.— The Sheet-Metal Worker's Instructor: 

* For Zinc, Sheet-Iron, Copper, and Tin-Plate Workers, etc. Contain- 
ing a selection of Geometrical ProKems ; also, Practical and Simple 
Rules for Describing the various Patterns required in the different 
branches of the above Trades. By Reuben H. Warn, Practical 
Tin-Plate Worker. To which is added an Appendix, containing 
Instructions for Boiler-Making, Mensuration of Surfaces and Solids, 
Rules for Calculating the Weights of different Figures of Iron and 
Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty- 
two Plates and thirty-seven Wood Engravings. 8vo. . #3-O0 

WARNER. — New Theorems, Tables, and Diagrams, for the 
Computation of Earth-work : 

Designed for the use of Engineers in Preliminary and Final Estimates, 
of Students in Engineering, and of Contractors and other non-profes. 
sional Computers. In two parts, with an Appendix. Part I. A Prac- 
tical Treatise; Part II. A Theoretical Treatise, and the Appendix. 
Containing Notes to the Rules and Examples of Part I.; Explana- 
tions of the Construction of Scales, Tables, and Diagrams, and a 
Treatise upon Equivalent Square Bases and Equivalent Level Heights. 
The whole illustrated by numerous original engravings, comprising 
explanatory cuts for Definitions and Problems, Stereometric Scales 
and Diagrams, and a series of Lithographic Drawings from Models : 
Showing all the Combinations of Solid Forms which occur in Railroad 
Excavations and Embankments. By John Warner, A. M., Mining 
and Mechanical Engineer. Illustrated by 14 Plates. A new, revised 
and improved edition. 8vo. . . ... . . $4.00 

WATSON.— A Manual of the Hand-Lathe : 

Comprising Concise Directions for Working Metals of all kinds, 
Ivory, Bone and Precious Woods ; Dyeing, Coloring, and French 
Polishing; Inlaying by Veneers, and various methods practised to 
produce Elaborate work with Dispatch, and at Small Expense. By 
Egbert P. Watson, Author of " The Modern Practice of American 
Machinists and Engineers." Illustrated by 78 engravings. $1.50 

WATSON. — The Modern Practice of American Machinists and 
Engineers 
Including the Construction, Application, and Use of Drills, LatVia 
Tools, Cutters for Boring Cylinders, and Hollow-work generally , with 
the most Economical Speed for the same ; the Results verified by 
Actual Practice at the Lathe, the Vise, and on the Floor. Together 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 2C . 

with Workshop Management, Economy of Manufacture, the Steam- 
Engine, Boiltrs, Gears, Belling, etc., etc. By Egbert P. Watson. 
Illustrated by eighty-six engravings. i2mo. . . . $2.50 

WATSON.— The Theory and Practice of the Art of Weaving 
by Hand and Power ■ 
With Calculations and Tables for the Use of those connected with the 
Trade. By John Watson, Manufacturer and Practical Machine 
Maker. Illustrated by large Drawings of the best Power Looms. 
8vo - ••••...... #6.00 

WATT.— The Art of Soap Making: 

A Practical Hand-book of the Manufacture of Hard and Soft Soaps, 
Toilet Soaps, etc., including many New Processes, and a Chapter on 
the Recovery of Glycerine from Waste Leys. By Alexander 
Watt. 111. i2mo $3.00 

WEATHERLY.— Treatise on the Art of Boiling Sugar, Crys- 
tallizing, Lozenge-making, Comfits, Gum Goods, 
And other processes for Confectionery, etc., in which are explained. 
in an easy and familiar manner, the various Methods of Manufactur- 
ing every Description of Raw and Refined Sugar Goods, as sold by 
Confectioners and others. i2mo. ..... $i-$Q- 

WIGHTWICK.— Hints to Young Architects: 
Comprising Advice to those who, while yet at school, are destined 
to the Prolession; to such as, having passed their pupilage, are about 
to travel ; and to those who, having completed their education, are 
about to practise. Together with a Model Specification involvii.g a 
great variety of instructive and suggestive matter. By Georgb 
WtGHTWicK, Architect. A new edition, revised and considerably 
enlarged ; comprising Treatises on the Principles of Construction 
and Design. By G. Huskisson Guillaume, Architect. Numerous 
illustrations. One vol. i2mo. ...... #2.00 

W ILL, — Tables of Qualitative Chemical Analysis. 

With an Introductory Chapter on the Course of Analysis. By Pro- 
.essor Heinrich Will, of Giessen, Germany. Third Americanj 
from the eleventh German edition. Edited by CHARLES F. HlMES. 
Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa. 

8VO. . . • fri.rQ 

WILLIAMS.— On Heat and Steam : 

Embracing New Views of Vaporization, Condensation, and Explc* 
sion. By Charles Wye Williams, A. I. C. E. Illustrated 8vo. 

$ 2 -5° 
WILSON.— A Treatise on Steam Boilers : 

Their Strength, Construction, and Economical Working. By Robert 

Wilson. Illustrated i2mo $2.50 

WILSON.— First Principles of Political Economy: 

With Reference to Statesmanship and the Progress of Civilization. 

By Professor W. D. Wilson, of the Cornell University. A new and 

revised edition. 121110 #1.50 



30 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

WOHLER.— A Hand-Book of Mineral Analysis : 

By F. WoHLER, Professor of Chemistry in the University of Gottin- 
gen. Edited by Henry B. Nason, Professor of Chemistry in the 
Renssalaer Polytechnic Institute, Troy, New York. Illustrated. 
i2mo $2, 50 

WORSSAM.— On Mechanical Saws : 

From the Transactions of the Society of Engineers. 1869. By S. W. 
Worssam, Jr. Illustrated by eighteen large plates. 8vo. #2.50 



RECENT ADDITIONS. 

BRANNT. — Varnishes, Lacquers, Printing Inks and Sealing - 
Waxes : 

Their Raw Materials and their Manufacture, to which is added the 
Art of Varnishing and Lacquering, including the Preparation of Put- 
ties and of Stains for Wood, Ivory, Bone, Horn, and Leather. By 
William T. Brannt. Illustrated by 39 Engravings, 338 pages. 
i2ino. .......... $3.00 

BRANNT — The Practical Scourer and Garment Dyer: 

Comprising Dry or Chemical Cleaning; the Art of Removing Stains; 
Fine Washing; Bleaching and Dyeing of Straw Hats, Gloves, and 
Feathers of all kinds; Dyeing of Worn Clothes of all fabrics, in- 
cluding Mixed Goods, by One Dip; and the Manufacture of Soaps 
and Fluids for Cleansing Purposes. Edited by William T. Brannt, 
Editor of " The Techno-Chemical Receipt Book." Illustrated. 
203 pages. i2mo. $2.00 

BRANNT.— The Metallic Alloys : 

A Practical Guide for the Manufacture of all kinds of Alloys, Amal- 
gams and Solders used by Metal Workers, especially by Bell Founders, 
Bronze Workers, Tinsmiths, Gold and Silver Workers, Dentists, etc., 
etc., as well as their Chemical and Physical Properties. Edited 
chiefly from the German of A. Krupp and Andreas Wildberger, with 
additions by Wm. T. Brannt. Illustrated. i2mo. $3-°° 

BRANNT. — A Practical Treatise on the Manufacture of Vine- 
gar and Acetates, Cider, and Fruit-Wines ; 
Preservation of Fruits and Vegetables by Canning and Evaporation ; 
Preparation of Fruit-Butters, Jellies, Marmalades, Catchups, Pickles, 
Mustards, etc. Edited from various sources. By WILLIAM T. 
Brannt. Illustrated by 79 Engravings. 479 pp. 8vo. $5.00 

BRANNT.— The Metal Worker's Handy-Book of Receipts 
and Processes : 

Being a Collection of Chemical Formulas and Practical Manipula- 
tions tor the working of all Metals; including the Decoration and 
Beautifying of Articles Manufactured therefrom, as well as their 
Preservation. Edited from various sources. By William T. 
Brannt. Illustrated. i2mo. $2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



DEITE. — A Practical Treatise on the Manufacture of Per- 
fumery : 
Comprising directions for making all kinds of Perfumes, Sachet 
Powders, Fumigating Materials, Dentifrices, Cosmetics, etc., with a 
full account of the Volatile Oils, Balsams, Resins, and other Natural 
and Artificial Perfume-substances, including the Manufacture of 
Fruit Ethers, and tests of their purity. By Dr. C. Deite, assisted 
by L. Borchert, F. Eichbaum, E. Kugler, H. Toeffner, and 
other experts. From the German, by Wm. T. Brannt. 28 Engrav- 
ings. 358 pages. 8vo. $3-°° 

LDWARDS. — American Marine Engineer, Theoretical and 
Practical : 
With Examples of the latest and most approved American Practice. 
By Emory Edwards. 85 illustrations. i2mo. . . $2.50 

EDWARDS. — 900 Examination Questions and Answers: 

For Engineers and Firemen (Land and Marine) who desire to ob- 
tain a United States Government or State License. Pocket-book 
form, gilt edge ........ $1-5° 

POSSELT.— Technology of Textile Design : 

Being a Practical Treatise on the Construction and Application of 
Weaves for all Textile Fabrics, with minute reference to the Litest 
Inventions for Weaving. Containing also an Appendix, showing 
the Analysis and giving the Calculations necessary for the Manufac- 
tuie of the various Textile Fabrics. By £. A. Posselt, Head 
Master Textile Department, Pennsylvania Museum and School of 
Industrial Art, Philadelphia, with over 1000 illustrations. 292 
pages. 4to. . . . . . . . . - $5- oa 

POSSELT. — The Jacquard Machine Analysed and Explained : 

With an Appendix on the Preparation of Jacquard Cards, and 
Practical Hints to Learners of Jacquard Designing. By E. A. 
Posselt. With 230 illustrations and numerous diagrams. 127 pp. 
4t"- • #3-°° 

POSSELT.— The Structure of Fibres, Yarns and Fabrics : 
Being a Practical Treatise for the Use of all Persons Employed in 
the Manufacture of Textile Fabrics, containing a Description of tl.fl 
Growth and Manipulation of Cotton, Wool, Worsted, Silk, Flax, 
Jute, Ramie, China Grass and Hemp, and Dealing with all Manu- 
facturers' Calculations for Every Class of Material, also Giving 
Minute Details for the Structure of all kinds of Textile Fabrics, and 
an Appendix of Arithmetic, specially adapted for Textile Purposes. 
By E. A. Posset.t. Over 400 Illustrations, quarto. . $10.00 

RICH. — Artistic Horse-Shoeing: 

A Practical and Scientific Treatise, giving Improved Methods of 
Shoeing, with Special Directions for Shaping Shoes to Cure Different 
Diseases of the Foot, and for the Correction of Faulty Action in 
Trotters. By George E. Rich. 62 Illustrations. 153 pages. 
121110 $1.00 



HENRY CAREY BATRD & CO.'S CATALOGUE. 



RICHARDSON.— Practical Blacksmithing : 

A Collection of Articles Contributed at Different Times by Skilled 
Workmen to the columns of " The Blacksmith and Wheelwright," 
and Covering nearly the Whole Range of Blacksmithing, from the 
Simplest Job of Work to some of the Most Complex Forging-;, 
Compiled and Edited by M. T. Richardson. 

Vol. I. 210 Illustrations. 224 pages. I2mo. . . $1.00 

Vol. II. 230 Illustrations. 262 pages. 121110. . . $1.00 
Vol. III. 390 Illustrations. 307 pages. l2mo. . . $1 00 

Vol. IV. 226 Illustrations. 276 pages. l2ino. , . $i.co 

RICHARDSON —The Practical Horseshoer: 

Being 3 Collection of Articles on Horseshoeing in all its Branche* 
which have appeared from time to time in the columns of " '1 he 
Blacksmith and Wheelwright," etc. Compiled and edited by M. T. 
Richardson. 174 illustrations #1.00 

ROPER. — Instructions and Suggestions for Engineers and 
Firemen : 
By Stephen Roper, Engineer. i8mo. Morocco . $2.00 

ROPER.— The Steam Boiler: Its Care and Management: 
By Stephen Roper, Engineer. i2mo., tuck, gilt edges. $2.00 

ROPER. — The Young Engineer's Own Book: 

Containing an Explanation of the Principle and Theories 011 which 
the Steam Engine as a Piime Mover is Based. By Stephen Roper, 
Engineer. 160 illustrations, 363 pages. i8mo., tuck . #3.00 

ROSE. — Modern Steam - Engines : 

An Elementary Treatise upon the Stearr-ICngine, written in Plain 
language ; for Use in the Workshop as well as in the Drawing Office. 
Giving Full Explanations of the Construction of Modern Stearr- 
Engines : Including Diagrams showing their Actual operation. To- 
gether with Complete but Simple Explanations of the operations of 
Various Kinds of Valves, Valve Motions, and Link Motions, etc., 
thereby Enabling the Ordinary Engineer to clearly Understand the 
Principles Involved in their Construction and Use, and to Plot out 
their Movements upon the Drawing Board. By Joshua Rose. M. E. 
Illustrated by 422 engravings. Revised. 358 pp. . . $6.00 

ROSE.— Steam Boilers: 

A Practical Treatise on Boiler Construction and Examination, for the 
Use of Practical Boiler Makers, Boiler Users, and Inspectors; and 
embracing in plain figures all the calculations necessary in Designing 
or Classifying Steam Boilers. By Joshua Rose, M. E. Illustrated 
by 73 engravings. 250 pages. 8vo. .... $2.^0 
SCHRIBER — The Complete Carriage and Wagon Painter: 
A Concise Compendium of the Art of Painting Carriages, Wagons.. 
and Sleighs, embracing Full Directions in all the Various Branches, 
including Lettering, Scrolling, Ornamenting, Striping, Varnishing, 
and Coloring, with numerous Recipes for Mixing Colors. 73 Illus- 
trations. 177 pp. 1 21110. . . . . • • $I.O(5 












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